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Biomedical subjects

D Fan

Publications and source records attributed to D Fan.

At least 91 records · Page 5Linked to original sources
PubMed1995

Antitumor effects of liposomal IL1 alpha and TNF alpha against the pulmonary metastases of the B16F10 murine melanoma in syngeneic mice.

Interleukin 1 alpha (IL1 alpha) and tumor necrosis factor alpha (TNF alpha) have been successfully incorporated into specific phosphatidylcholine (PC) and phosphatidylserine (PS) multilamellar vesicle (MLV) liposomes by modifying the concentration of calcium ion and pH of the encapsulation buffer. Under these conditions, some of the cytokines may attach to the exterior surface of the MLV and therefore be readily accessible to target cells for receptor binding and signal transduction. These cytokine-associated liposomes are stable for up to 2 weeks in serum-free buffer, and leakage of cytokines into medium containing 10% fetal bovine serum was about 50% at the end of a 3-day incubation period at 37 degrees C. The biological activities mediated by liposomal IL1 alpha and TNF alpha were specific: the stimulation of thymidine uptake in T-helper D10 lymphocytes and the cytolysis of TNF alpha-sensitive L929 target cells could be blocked by specific neutralizing antibodies in a dose-dependent fashion. When administered intravenously into C57BL/6 mice bearing the syngeneic B16F10 murine melanoma cells, dual entrapment of liposomal IL1 alpha and TNF alpha significantly reduced the number of metastatic tumor nodules in the lungs and prolonged the life span of the animals. Thus, liposomal IL1 alpha and TNF alpha displayed significant in vivo antitumor activity against the IL1 alpha- and TNF alpha-resistant B16F10 metastatic murine melanoma.

Animals↗
PubMed1995

Ligation of the thoracic duct without thoracotomy as an effective treatment for postoperative chylothorax: a newly designed surgical procedure.

We describe herein a newly designed surgical procedure for ligating the thoracic duct to treat postoperative chylothorax, without performing a thoracotomy. This technique was successfully performed on a 50-year-old man who developed chylothorax following resection of carcinoma of the esophagus whose case is briefly presented. The advantages of this procedure include the following: the integrity of the thorax is maintained, there is less traumatization, the need for a drainage tube is eliminated, shorter hospitalization is required, and the thoracic duct is much more easily exposed than by conventional transthoracic approaches. No similar report was found in our research of the literature.

Chylothorax↗
PubMed1995

Treatment of nude mice with 4-amidinoindan -1- one2 '- amidinohydrazone, a new S-adenosylmethionine decarboxylase inhibitor, delays growth and inhibits metastasis of human melanoma cells.

CGP 48664A (4-amidinoindan-1-one2'-amidinohydrazone) is a novel inhibitor of S-adenosyl-methionine decarboxylase (SAMDC), a key enzyme in the biosynthesis of polyamines, which are themselves essential for proliferation of mammalian cells. Seven different human melanoma cell lines were treated in vitro with CGP 48664A. High, intermediate and low levels of cytostasis were induced in four, one and two melanoma lines, respectively. This cytostasis was reversed by the addition of exogenous spermidine or spermine to the culture medium. The heterogeneous low metastatic (CGP 48664A-resistant) A375P cells and highly metastatic (CGP 48664A-sensitive) A375SM cells were implanted into the subcutis or injected intravenously into nude mice. Systemic daily administration of CGP 48664A significantly reduced the size of cutaneous lesions and the number of lung metastases in mice implanted with A375SM cells. No beneficial effects were found in mice injected with A375P cells. Drug activity was dose dependent, and maximal effects were observed when treatment began in mice with small tumour burdens. The data suggest that CGP 48664A is effective against melanoma metastasis in nude mice and that its activity should be tested in combination with other cytoreductive agents.

Adenosylmethionine Decarboxylase↗
PubMed1995

Hypertension prevalence and status of awareness, treatment and control in China.

A nation-wide survey of blood pressure (BP) and high BP was made in China in 1991, using standardized methods and covering 950,356 men and women aged 15 years and above, from 30 provinces, autonomous regions, and municipalities. The purpose of the study was to estimate the prevalence and the status of awareness, treatment, and control of hypertension. The overall prevalence rate of hypertension defined as systolic BP > or = 140 or diastolic BP > or = 90 mmHg or currently on antihypertensive medication was 13.6%, and was higher in urban (16.3%) than in rural (11.1%) setting. The rate was 6.6% if a BP cut-point of 160/95 mmHg was used. Rates were low in younger age-groups but rose sharply after age 45. The total number of hypertensives in 1990 was estimated to be close to 90 millions. Of all hypertensives, about 1/4 were aware of their high BP, half of these were on medication, and only 3% had their BP controlled. All the rates were higher if the BP cut-point was 160/95 mmHg. Higher rates were found in urban than rural setting and, to a lesser degree, for women than men. In conclusion, hypertension was found to be common in China, and the rates of awareness, drug treatment, and controlled BP were low, indicating an urgent need for developing a national program of treatment and prevention of high BP.

Adolescent↗
PubMed1995

Isolation and characterization of metastatic variants from human transitional cell carcinoma passaged by orthotopic implantation in athymic nude mice.

PURPOSE: These studies were designed to develop an orthotopic model for human bladder cancer and to isolate variant metastatic cell lines. MATERIALS AND METHODS: The human bladder cancer cell line 253J was implanted into the muscular wall of the bladder of athymic nude mice. By in vivo recycling, we selected for 2 variant cell lines: 253J B-V, a bladder line isolated after 5 serial passages in the bladder, and 253J lung-IV, established from a lung tumor nodule that was recycled through the bladder. RESULTS: These 2 cell lines showed enhanced tumorigenicity, as measured by a decreased latent period, and rapid growth as compared with the parental cell line. Moreover, orthotopic implantation of these cell lines resulted in metastasis to the lungs. These in vivo-selected, metastatic cell lines exhibited unique karyotypic alterations, increased anchorage-independent growth, overexpression of basic fibroblast growth factor, altered expression of adhesion molecules and the ability to migrate through Matrigel. CONCLUSIONS: This reproducible model of human bladder cancer offers the opportunity to study cellular properties associated with tumor progression and metastasis and is suitable for the evaluation of new therapeutic strategies for invasive bladder cancer.

Animals↗
PubMed1995

Mechanical efficiency of stunned myocardium is modulated by increased afterload dependency.

OBJECTIVE: Oxygen consumption (MVO2) of stunned myocardium is relatively high compared to, and poorly correlated with, systolic contractile function. The aim of this study was to investigate whether an increased afterload dependency, induced by the decreased contractility of the stunned myocardium, contributes to the large variability in the mechanical efficiency data. METHODS: In 13 anaesthetised open thorax pigs undergoing two cycles of 10 min occlusion of left anterior descending coronary artery and 30 min reperfusion, segment shortening, the slope of end systolic pressure segment length relationship (Ees), external work (EW, derived from the area inside the left ventricular pressure segment length loop), the efficiency of energy conversion (EET, = EW/PLA x 100%, where PLA = total pressure-segment length area), mechanical efficiency (EW/MVO2), and their dependency on left ventricular end systolic pressure (Pes) were determined before and after induction of stunning, and during subsequent inotropic stimulation with dobutamine (1 and 3 micrograms.kg-1.min-1 over 15 min). RESULTS: The stunning protocol not only caused significant decreases in segment shortening, external work, energy conversion efficiency, and EW/MVO2 but also increased the afterload dependency of these variables. Before stunning an increase in Pes from 100 to 160 mm Hg decreased segment shortening from 18(SEM 1)% to 14(2)% (P > 0.05) and increased external work from 206(18) to 254(32) mm Hg.mm (P < 0.05). After induction of stunning the same increase in Pes caused a decrease in segment shortening from 9.5(1.8)% to -4.6(2.1)% (P < 0.05) and in external work from 149(21) to -11(10) mm Hg.mm (P < 0.05). The afterload dependency of the PLA was not altered by stunning, but the afterload dependency of energy conversion efficiency increased, since efficiency decreased from 67(3)% to 59(5)% as Pes was increased from 100 to 160 mm Hg before stunning, but from 57(5) to -7(5)% after induction of stunning (P < 0.05). Furthermore, the same increase in Pes resulted in an 8% decrease of EW/MVO2 before stunning and 107% after induction of stunning. Infusion of dobutamine not only restored segment shortening, external work, energy conversion efficiency, and EW/MVO2 of the stunned myocardium, but also attenuated their afterload dependency to pre-stunning levels. CONCLUSIONS: Myocardial stunning increases the afterload dependency of segment shortening, external work, energy conversion efficiency, and mechanical efficiency, which can be attenuated by inotropic stimulation with dobutamine. However, the decrease in left ventricular end systolic pressure, which accompanies the induction of stunning, counteracts the decrease in these variables. These two mechanisms can explain most of the reported scatter in mechanical efficiency.

Animals↗
PubMed1995

The antitumor activity of doxorubicin against drug-resistant murine carcinoma is enhanced by oral administration of a synthetic staurosporine analogue, CGP 41251.

We evaluated the therapeutic efficacy against murine drug-sensitive and drug-resistant tumor of a combination chemotherapy regimen comprising intravenous administration of doxorubicin (DXR) plus oral administration of the staurosporine analogue CGP 41251 (benzoylstaurosporine), a highly specific inhibitor of protein kinase C (PKC). In vitro studies indicated that the simultaneous presence of noncytotoxic concentrations of CGP 41251 with DXR decreased the median inhibitory concentration (IC50) about 3-fold in the drug-sensitive parental murine cell lines, CT-26P and UV2237. Similar treatment of drug-resistant variants of these tumor cell lines reversed their multiple drug resistant (MDR) phenotype (about a 5-fold increase in their sensitivity to DXR) and increased the cellular accumulation of DXR. Combination therapy in vivo with DXR and CGP 41251 significantly inhibited the SC growth of the drug-resistant CT-26R500 cell line. This effect was confirmed by the ability of this combination therapy to reduce the number of lung metastases produced by IV injection of either the drug-sensitive parental line CT-26P or the drug-resistant subline, CT-26R500. PKC activity was reduced in tumors derived from mice treated with either DXR or CGP 41251, but not from those derived from mice treated with the combination. These results reflect one of the infrequent examples of being able to modulate the sensitivity of in vivo-grown tumors to the antitumor effects of an MDR-related drug and suggest a basis for evaluation of CGP 41251 in clinical trials.

Administration, Oral↗
PubMed1995

Level and function of epidermal growth factor receptor predict the metastatic potential of human colon carcinoma cells.

The purpose of this study was to determine whether production of liver metastasis by human colon carcinoma (HCC) cells depends on the response of tumor cells to organ-derived growth factors. HCC cells were isolated from several surgical specimens whose malignant potential differed (Dukes' stage B or D tumors), adapted to grow in culture, and assessed for expression of the epidermal growth factor receptor (EGF-R). Northern blot analyses revealed that highly metastatic HCC cells expressed >5-fold the number of EGF-R mRNA transcripts as low metastatic cells. The level of mRNA correlated with the amount of EGF-R protein as detected by Western blotting, immunohistochemistry, and Scatchard analyses. HCC growth response in vitro to picograms of transforming growth factor alpha was associated with functional cell surface EGF-Rs as determined by receptor tyrosine kinase activity assays. The EGF-R gene was not amplified or rearranged in highly metastatic cells. However, fluorescence in situ hybridization analysis showed that the copy number of chromosome 7 was higher in the highly metastatic cells. HCC cells were selected in vitro for low or high expression of EGF-R. Subsequent to injection into nude mice, only cells with high expression of EGF-R produced a high incidence of liver metastasis. These data demonstrate that expression of EGF-R by HCC cells directly correlates with their ability to produce hepatic metastasis.

Animals↗
PubMed1994

Evidence that protein kinase C-alpha activation is a critical event in phorbol ester-induced multiple drug resistance in human colon cancer cells.

We previously designed and characterized an in vitro model of the intrinsic drug resistance of human colon cancer. The human colonic epithelium is chronically exposed to endogenous protein kinase C (PKC) stimulatory factors, and our model demonstrated that activation of PKC induces resistance to multiple anticancer drugs in the metastatic human colon cancer cell line KM12L4a. PKC is an isozyme family with ten members, eight of which are phorbol ester-responsive. In this report, we show that thymeleatoxin (Tx), a daphnane tumor promoter that selectively activates the phorbol ester-responsive isozymes cPKC-alpha, -beta 1, -beta 2, and -gamma, was just as effective in inducing drug resistance in KM12L4a cells as phorbol dibutyrate, a potent activator of all phorbol ester-responsive PKC isozymes. The induction of resistance by Tx was associated with a reduction in cytotoxic drug accumulation in KM12L4a cells. We demonstrated by immunoblot analysis and hydroxylapatite chromatography that KM12L4a cells express active cPKC-alpha but not cPKC-beta 1, -beta 2, or gamma. Our results provide strong evidence that phorbol-ester activation of cPKC-alpha is sufficient for the induction of resistance observed in KM12L4a cells. The possibility that endogenous PKC activators may induce intrinsic drug resistance in clinical colon cancer by an analogous mechanism is strongly suggested by our detection of active cPKC-alpha in surgical specimens of human colon carcinomas.

Colonic Neoplasms↗
PubMed1994

Role of domain 3 of calmodulin in activation of calmodulin-stimulated phosphodiesterase and smooth muscle myosin light chain kinase.

CaM[3 TnC] is a calmodulin-cardiac troponin C chimeric protein containing the first, second, and fourth calcium-binding domains of calmodulin (CaM) and the third calcium-binding domain of cardiac troponin C (cTnC) (George, S. E., Su, Z., Fan, D., and Means, A. R. (1993) J. Biol. Chem. 268, 25213-25220). CaM[3 TnC] shows altered activation of phosphodiesterase (PDE) and is a potent competitive inhibitor of smooth muscle myosin light chain kinase (smMLCK) activation by CaM. To determine why CaM[3 TnC] exhibits altered target enzyme interactions, we constructed a series of domain 3 CaM mutants. We began with subdomain substitutions, replacing most of CaM's helix 5, Ca2+ binding loop 3, and helix 6 with the corresponding subdomains of cTnC. Only CaM[helix 6-TnC] exhibited significant impairment of smMLCK and PDE activation. We then individually substituted the residues in the region of CaM's helix 6 with the corresponding cTnC residue. This revealed that CaM residues Thr-110, Leu-112, and Lys-115 were critical for full smMLCK activation and could not be substituted by the corresponding cTnC residue (Gln, Thr, and Thr, respectively). In contrast, only the L112T substitution significantly affected PDE activation. The CaM-smMLCK peptide structure (Meador, W. E., Means, A. R., and Quiocho, F. A. (1992) Science 257, 1251-1255) suggests a relationship between the proposed helix 6 smMLCK-activating residues and those previously described in helix 2 (VanBerkum, M. F. A., and Means, A. R. (1991) J. Biol. Chem. 266, 21488-21495).

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1994

Organ-specific modulation of steady-state mdr gene expression and drug resistance in murine colon cancer cells.

BACKGROUND: The major cause of death from cancer is metastases that are resistant to conventional therapies. The resistance of metastatic tumor cells to chemotherapy can be caused by their intrinsic properties, such as increased expression of the mdr genes. PURPOSE: The purpose of our present study was to determine some of the mechanisms by which the organ microenvironment influences the response of tumor cells to chemotherapy. METHODS: Murine CT-26 colon cancer cells growing in continuous culture (parental cells) were harvested and injected subcutaneously into the lateral flank (to produce subcutaneous tumors) or the lateral tail vein (to produce experimental lung metastases) of 10 8-week-old syngeneic male BALB/c mice. Seven days after tumor-cell injection, the mice were given intravenous injections of either doxorubicin (10 mg/kg) or 0.9% NaCl (controls). This in vivo injection was repeated 7 days later. Mice with subcutaneous tumors and lung metastases were killed by cervical dislocation on day 21, and tumor samples from control mice were harvested and adapted to culture. The sensitivity of the cultured cells to doxorubicin and fluorouracil (5-FU) was determined at multiple time points. Levels of mdr-1 DNA were measured by slot-blot and Southern-blot analyses. mdr mRNA expression levels were measured by Northern-blot analysis using mdr-1- and mdr-3-specific hybridization probes, and P-glycoprotein level was determined by fluorescence-activated cell sorting using different monoclonal antibodies. RESULTS: Treatment with doxorubicin produced 80% growth inhibition of CT-26 subcutaneous tumors but had little effect on the number (and size) of experimental lung metastases. Collectively, the results suggest that the multidrug-resistant phenotype developed in CT-26 cells growing in the lung environment. Cultures established from lung metastases were initially resistant to doxorubicin (but not to 5-FU) and showed elevated expression of mdr-1 mRNA transcripts and P-glycoprotein. This resistance could be overcome by verapamil and disappeared after 21 days in culture. No mdr gene amplification was detected. The expression level of mdr-specific mRNA (predominance of mdr-1) and P-glycoprotein was directly associated with resistance to doxorubicin. CONCLUSIONS: Results of this study have demonstrated that the in vivo sensitivity of murine CT-26 colon carcinoma cells to doxorubicin depends on the organ environment. The organ environment can influence the P-glycoprotein-mediated multidrug-resistant phenotype in tumor cells, and the increased expression of P-glycoprotein is transient; once removed from the environment (lung), the cell's resistance reverts to that of the sensitive parent cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Modulation of tumor cell response to chemotherapy by the organ environment.

The outcome of cancer metastasis depends on the interaction of metastatic cells with various host factors. The implantation of human cancer cells into anatomically correct (orthotopic) sites in nude mice can be used to ascertain their metastatic potential. While it is clear that vascularity and local immunity can retard or facilitate tumor growth, we have found that the organ environment also influences tumor cell functions such as production of degradative enzymes. The organ microenvironment can also influence the response of metastases to chemotherapy. It is not uncommon to observe the regression of cancer metastases in one organ and their continued growth in other sites after systemic chemotherapy. We demonstrated this effect in a series of experiments using a murine fibrosarcoma, a murine colon carcinoma, and a human colon carcinoma. The tumor cells were implanted subcutaneously or into different visceral organs. Subcutaneous tumors were sensitive to doxorubicin (DXR), whereas lung or liver metastases were not. In contrast, sensitivity to 5-FU did not differ between these sites of growth. The differences in response to DXR between s.c. tumors (sensitive) and lung or liver tumors (resistant) were not due to variations in DXR potency or DXR distribution. The expression of the multidrug resistance-associated P-glycoprotein as determined by flow cytometric analysis of tumor cells harvested from lesions in different organs correlated inversely with their sensitivity to DXR: increased P-glycoprotein was associated with overexpression of mdr1 mRNA. However, the organ-specific mechanism for upregulating mdr1 and P-glycoprotein has yet to be elucidated.

Animals↗
PubMed1994

Reversal of multidrug resistance in murine fibrosarcoma cells by thioxanthene flupentixol.

The purpose of this study was to identify calcium channel and calmodulin antagonists effective in increasing the cytotoxic effects of several chemotherapeutic drugs against UV-2237 murine fibrosarcoma MDR cells. Among 8 compounds tested at nontoxic concentrations, flupentixol, a piperazine-substituted thioxanthene, was the most potent in enhancing the cytotoxicity of anticancer drugs commonly associated with the multidrug resistant (MDR) phenotype, such as Adriamycin, actinomycin D, vinblastine, and vincristine, but not 5-fluorouracil, a drug usually unaffected by MDR. The chemosensitizing effects of flupentixol were produced by increasing intracellular drug accumulation via a mechanism unrelated to the binding of the plasma membrane P-glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Determination of oxygen permeability and volumetric oxygen transfer rate of shaken flasks.

The oxygen permeability passing through the gauze layer and the actual and apparent volumetric oxygen transfer rate, KLa and (KLa)app, respectively, were determined in specially designed Erlenmeyer flasks, which have an oxygen electrode inserted in the middle part of flasks. The oxygen transfer rate was determined by sulfite oxidation. As a result, the oxygen permeability passing through 8 layers of gauze at 37 degrees C, 220 rpm, with 50 ml sulfite solution in a 500-ml flask was 43.7 mol/m.h atm; as the oxygen partial pressure decreased by 6.1%, the value of KLa increased by 100%; the relationship between rotational speed of shaker, n(rpm); volume of flask, V(ml); liquid content in flask, VL(ml); temperature of shaker, t(degrees C) and KLa, as well as (KLa)app (1/h) were: [formula: see text]

Chemical Engineering↗
PubMed1994

Organ site-dependent expression of basic fibroblast growth factor in human renal cell carcinoma cells.

We investigated the influence of organ microenvironment on the angiogenic phenotype in human renal cell carcinoma (HRCC) cells. HRCC line SN12C was established in vitro from a surgical specimen, and metastatic line SN12PM6 was isolated from a lung metastasis produced by parental cells implanted into the kidney of nude mice. SN12C (low metastasis) and SN12PM6 (high metastasis) cells were injected into the kidney or subcutis of nude mice. The kidney tumors were highly vascularized (as revealed by immunohistochemistry using antibodies against factor VIII), and metastatic, whereas the subcutaneous tumors were not. The expression of mRNA for basic fibroblast growth factor (bFGF) in kidney tumors was 10 to 20 times that found in subcutaneous tumors. Similar data were obtained at the protein level by using fluorescence activated cell sorting, immunohistochemistry, and enzyme-linked immunosorbent assay. bFGF was detected in the urine of mice with tumors in the kidney but not subcutaneous tumors. The level of bFGF in the serum of mice with kidney tumors was two to three times that in mice with subcutaneous tumors. The changes in bFGF expression in the tumors was transient. Collectively, these data indicate that the organ microenvironment can influence the expression level of bFGF in HRCC.

Animals↗