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Biomedical subjects

X Tong

Publications and source records attributed to X Tong.

At least 55 records · Page 3Linked to original sources
PubMed1999

Computer simulation of particle separation based on non-equilibrium swelling.

Steric/hyperlayer field-flow fractionation (FFF) is an established analytical technique for separating and characterizing particles in the 1-100 microns diameter range. The separation can be based on differences in size, density, shape and mechanical properties of the particles. In the course of an analysis of the water transporter system of Chinese hamster ovary (CHO) cells and one of their high permeability mutants, the first successful attempt was made to use the steric/hyperlayer FFF system for the purpose of separating particles based on a time-dependent property, namely, the differential swelling of the two cell types. The present study was undertaken to simulate numerically the separation and suggest selection of operating conditions to minimize repetitive experiments. The computer simulation was developed using Maple V, a symbolic computing environment. It is shown that the model is able to predict an optimal velocity of carrier buffer that maximizes resolution. Predicted velocity/resolution pairs are in good agreement with available experimental data. Empirical models for the lift forces encountered in such FFF experiments, and for the zone broadening observed in work with cell sized particles, form the basis for this model.

Animals↗
PubMed1999

Characterization of a technique for rapid pharmacokinetic studies of multiple co-eluting compounds by LC/MS/MS.

A method for rapid pharmacokinetic screening of multiple potential drug candidates has been developed. This technique, based on the ability of liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) to independently monitor multiple components, enables the quantification of substances which may or may not be chromatographically resolved. Our results indicate that the limit of quantitation and accuracy of this multiple-compound LC/MS/MRM quantitation method are comparable to a single-compound LC/MS/MRM quantitation method. No apparent ion suppression due to the existence of extraneous compounds in the analytical solution and biological matrix effect are observed in the range of the calibration curve. The issue of potential residual molecule cross-talk interference existing in the multiple-reaction monitoring mode has been discussed. This multiple-compound LC/MS/MRM quantitation method can be used for high throughput pharmacokinetic screening and to assay mixtures that have co-eluting analytes or similar m/z of precursor/product ion pairs.

Animals↗
PubMed1999

Comparison of long-term survival of cytomegalovirus promotre versus Rous Sarcoma virus promoter-driven thymidine kinase gene therapy in nude mice bearing human ovarian cancer.

The cytomegalovirus (CMV) promoter is considered one of the strongest positive regulators leading to expression of higher levels of the thymidine kinase (TK) enzyme than the Rous Sarcoma virus (RSV) promoter in vitro and in vivo. Cell killing efficacy of adenovirus-mediated CMV promoter-driven herpes simplex virus (HSV) TK gene therapy has been found to be 2 to 10 times more effective than RSV driven HSV-TK gene therapy in vitro. In this study the impact of CMV- versus RSV-driven HSV-TK gene therapy on long-term survival of nude mice bearing human ovarian cancer has been evaluated using a prospective randomized experimental design. The experiment was designed to show significance of survival differences from a 50% increase of survived days at a p-value of 0.05 with a power of 80%. All treatment groups showed an increase in median survival compared with control groups. Treatment benefit was ADV/CMV-TK vector dose dependent. At a given viral dose, no significant prolongation of survival was observed comparing CMV- and RSV-driven ADV-TK indicating that simply increasing cell killing efficacy in vitro above a minimal threshold level using a stronger promoter may not lead to prolongation of survival in the HSV-TK/GCV system.

Adenoviridae↗
PubMed1999

Contribution of endogenous carbon monoxide to regulation of diameter in resistance vessels.

Endogenous carbon monoxide was proposed to subserve vasodepressor functions. If so, inhibition of heme oxygenase may be expected to promote vascular contraction. This hypothesis was examined in large and small arteries and in isolated first-order gracilis muscle arterioles of rat. The heme oxygenase inhibitors chromium mesoporphyrin (CrMP) and cobalt protoporphyrin (0.175-102 micromol/l) decreased the diameter of pressurized (80 mmHg) gracilis muscle arterioles, whereas magnesium protoporphyrin, a weak heme oxygenase inhibitor, did not. CrMP also elicited development of isometric tension in the muscular branch of the femoral artery but not in the aorta or femoral artery. Arteriolar constrictor responses to CrMP varied in relation to the intravascular pressure, were blunted in preparations exposed to exogenous carbon monoxide (100 micromol/l), and were unaffected by an endothelin receptor antagonist. Importantly, CrMP amplified the constrictor response to increases of pressure in gracilis arterioles. Accordingly, the constrictor effect of heme oxygenase inhibitors is attributable to magnification of myogenic tone due to withdrawal of a vasodilatory mechanism mediated by endogenous carbon monoxide. The study suggests that the vascular carbon monoxide system plays a role in the regulation of basal tone in resistance vessels.

Animals↗
PubMed1999

[Expression of endothelin-1 and endothelin-1 mRNA in placental villus of pregnancy induced hypertension and the changes of plasma endothelin-1].

OBJECTIVE: To investigate the role of endothelin (ET-1) in the pathogenesis of pregnancy induced hypertension (PIH). METHODS: In 70 cases of PIH the plasma concentration of ET-1 was measured by RIA, and the expressions of ET-1 and its mRNA in placental villus were determined by immunohistochemistry and in situ hybridization respectively. 30 normal pregnant women (NP) served as control group. RESULTS: (1) The Plasma concentration of ET-1 was significantly higher in PIH than that in NP. There was a positive correlation between the plasma ET-1 level and mean arterial pressure in PIH. (2) The expressions of ET-1 and ET-1 mRNA were found in syncytiotrophoblast of placental villus and in the endothelium of fetal vessels. These positive signals were higher in PIH than in NP. CONCLUSION: The injury of endothelium of fetal and placental blood vessels was one of the causes of PIH. The placenta may play an important role in the pathogenesis of PIH.

Adult↗
PubMed1999

[Serum concentration of interleukin-6 in maternal serum and its expression in amniochorionic membranes of preterm premature rupture of membrane].

OBJECTIVE: To investigate the relationship between interleukin-6 (IL-6) and preterm premature rupture of membranes (PPROM). METHODS: Serum IL-6 in 20 cases of normal pregnancy (control group) and 30 cases with PPROM in which 14 had moderate and severe chorioamnionitis (group 1), 16 had no chorioamnionitis (group 2) were measured by enzyme-linked immunosorbent assay (ELISA), and IL-6 protein in fetal membranes were determined by immunohistochemistry technique. RESULTS: The level of serum IL-6 in group 1 (155.17 ng/L) was significantly higher than that in group 2 (79.11 ng/L) and control group (70.15 ng/L) (P < 0.01). Expression of the IL-6 had more positive signs in chorion with chorioamnionitis, especially in infiltrating inflammatory cells. CONCLUSION: IL-6 associated with the onset of preterm labor caused by infection.

Extraembryonic Membranes↗
PubMed1999

[Study of autoimmunity in progeny of pregnant women with systemic lupus erythematosus].

OBJECTIVE: To study the effect of systemic lupus erythematosus (SLE) on physical, mental development and plasma antibody level of SLE in their progenies. METHODS: Routine physical examinations of 49 children from 48 SLE mothers were conducted. Compared immuno-fluorescence anti-nuclear antibody (IFANA), anticardiolipin (ACL), extractable nuclear antigen (ENA) and anti-ds-DNA plasma levels of SLE mothers and their progenies with that levels during pregnancy and in umbilical blood. RESULTS: The physical development (height and weight) in 47 out of 49 children were within normal range while the remaining 2 were in the lower limit. The autoimmune antibodies were all negative in the umbilical blood with autoimmune negative mothers, while the anti-ribonucleoprotein (anti-RNP), anti-Smith surface antigen (anti-SSA), anti-specific soluble ribonucleic acid (anti-SSB) and ACL could be transferred to fetus through placenta. During follow up study, compared the autoimmune positive rates in progenies with that of mothers, the positive rates of IFANA and anti-ds-DNA decreased significantly (P < 0.01), while no changes in ACL. Compared the autoimmune positive rates in progenies with that of their own umbilical levels, the positive rates of IFANA, anti-RNP, anti-SSA decreased significantly (P < 0.01), while no difference existed in ACL. Boys showed faster disappearance of autoimmune positive rates than that of girls. CONCLUSIONS: SLE did not show significant effects on the physical development of their progenies. Most autoimmune antibodies existed in umbilical blood were transferred through placenta during pregnancy and would disappear within 9 years after birth. Autoimmune antibodies decreased quicker in boys, and it indicated that girls should be follow-up more carefully. Autoimmune antibodies in the umbilical blood is an easy method for the screening of SLE progeny.

Adult↗
PubMed1999

[Study on tumor necrosis factor and pathogenesis of pregnancy induced hypertension].

OBJECTIVE: To study the role of tumor necrosis factor (TNF-alpha) in the pathogenesis of pregnancy induced hypertension (PIH). METHODS: Radioimmunoassay was used to measure the levels of TNF-alpha in 25 severe PIH patients and 25 normal pregnant women. Umbilical vein endothelial cells were cultured with TNF-alpha (500 U/ml) or without TNF-alpha. The concentration of endothelin-1 (ET-1), 6-ket-PGF1 alpha, nitrite (NO2-), expression of fibronectin(FN) and white blood cells adhesion to the surface of endothelial cells test were measured. RESULTS: The levels of TNF-alpha in serum of severe PIH patients were significantly higher than that of normal pregnant women (P < 0.05). In endothelium culture supernatant with TNF-alpha group, synthesis of ET-1, NO2- and 6-ket-PGF1 alpha increased, expression of FN on the surface of endothelial cells decreased, white blood cells adhesion to endothelial cells increased. There was significant difference between TNF-alpha group and control group. CONCLUSION: TNF-alpha may be involved in the pathogenesis of PIH.

6-Ketoprostaglandin F1 alpha↗
PubMed1999

[Colorectal cancer: lymphatic metastasis and choice of operation].

OBJECTIVE: To study lymphatic metastasis of colorectal cancer for deceding the of dissection extent of dissection. METHODS: Six hundred and twenty-three lymph nodes from 74 cases of colorectal cancer were analyzed after D(3) resection. They were classified into peritumor, longitudinal spread, and upward spread groups. The metastasis rate of lymph node and its incidence were calculated. RESULTS: The metastasis rate of lymph node and its incidence in the peritumor, longitudinal spread, and upward spread (N(2) and N(3)) groups were 47.2% and 38.6%, 22.8% and 18.6%, and 29.7% (20.3% and 9.4%) and 10.2% (19.0% and 5.3%), respectively. The distribution rate of metastatic lymph node was 61.2%, 17.1%, and 21.6% in the peritumor, longitudinal spread, and upward spread groups, respectively. Within 2.0 cm on the anal side of rectal cancer, the metastasis rate was 3.7%, whereas in 2.0 - 4.0 cm no metastasis was observed cancer at the lower part of the rectum demonstrated a higher lateral metastasis rate. CONCLUSIONS: Colorectal cancer tends to metastasize to longitudinal and the risk of metastasis increased in the stage of pT(3) and pT(4) or low differentiation stage. Jump metastasis is also a feature. D(3) radical resection is necessary for colorectal cancer, but extended lateral lymph node needs enectomy or total mesorectal excision. No residual tumor tissue exists at the anastomosis site after low anterior resection when the excision distance is beyond 2.0 cm from the anal margin of rectal cancer.

Adult↗
PubMed1999

[A dynamic study of influences of TMJOA on TMJ disc].

OBJECTIVE: To learn the changes of TMJ disc positions under the influences of TMJ Osteoarthrosis(TMJOA). METHODS: The TMJOA experimental animal model was established by 12 goats. The TMJ disc positions were observed and recorded at different intervals, (1 month, 2 months, 3 months, 4 months and 6 months) then the pathological changes of TMJ specimens were also studied. RESULTS: Significant anteromedial shift of TMJ disc position was observed in some certain TMJOA phases and became more obviously along with the disease progress. CONCLUSION: The shift of TMJ disc may be the secondary change of TMJOA.

Animals↗
PubMed1999

[Studies on the supercritical-CO2 fluid extraction and quality evaluation of ginger oils].

Essential oils from the dried rhizomes of Zingiber officinale were extracted by supercritical-CO2 fluid(SFE-CO2) and traditional water still distillation (WSD) methods, and the SFE extraction technology and quality (GC-MS, etc.) of the oils were studied. The results showed that the SFE-CO2 contains 49 constituents, such as 6-paradol, etc, the ginger peppery component of them gets to 22.90%.

Carbon Dioxide↗
PubMed1998

Total glycolipid and glucosylceramide content in serum and urine of patients with Gaucher's disease type 3 before and after enzyme replacement therapy.

The follow-up of Gaucher's patients under enzyme replacement therapy is generally based both on the clinical aspects and the evaluation of haematological parameters: haemoglobin level, platelet count, acid and alkaline phosphatase activities. Spleen and liver volumes are also reliable criteria for evaluating the improvement of the patients. The determination of glycolipid excretion in the urine and/or the quantification of glycolipids in serum can also be a useful tool for the screening and the follow up of patients with lysosomal storage disease including Gaucher's disease. In this paper we report the follow-up of three patients with Gaucher type 3; in order to test the efficacy of the enzyme replacement therapy with alglucerase in these patients, we evaluated the urine and plasma glucosylceramide content as a marker parallel to the clinical improvement and the decreased organomegaly.

Child↗
PubMed1998

Comparison of single- and repeated-dose pharmacokinetics of diazepam.

PURPOSE: To determine whether repeat boluses of diazepam (DZP) lead to significant accumulation in the central nervous system and/or peripheral compartments, as repeat intravenous boluses of diazepam are commonly used in the treatment of status epilepticus (SE). METHODS: In a rat model that permits simultaneous serum and cerebrospinal fluid (CSF) sampling, we characterized the pharmacokinetics of DZP and its metabolite, desmethyldiazepam, in CSF and blood using HPLC. DZP was administered by intraperitoneal injection as either a single dose (20 or 30 mg/kg) or repeat doses (10 or 20 mg/kg x 3, 1 h apart). RESULTS: After a single intraperitoneal dose, DZP was rapidly absorbed with a time to maximum concentration of 10 min. The serum concentrations then declined biexponentially. DZP rapidly entered the CSF, the CSF to serum ratio reached equilibrium within 10 min, and was equivalent to the ratio of free to total serum concentration. Repeated DZP dosing resulted in a threefold decrease in volume of distribution and clearance (p < 0.001). This was reflected in the CSF concentration data; however, after the third dose, the ratio of CSF to serum concentration, also increased greatly, representing further persistence of DZP in the CSF compartment. CONCLUSIONS: Repeat dosing of DZP leads to substantial accumulation, and high, persistent serum and CSF concentrations, which may explain the toxic effects of repeat DZP dosing. Repeat dosing of DZP using a tapering protocol, however, may increase the effectiveness of DZP in treating SE by preventing relapses without substantially increasing toxicity.

Animals↗
PubMed1998

Interaction of the bovine papillomavirus E6 protein with the clathrin adaptor complex AP-1.

The E6 gene of the bovine papillomavirus type 1 (BPV-1) is expressed in fibropapillomas caused by BPV-1 and in tissue culture cells transformed by BPV-1. It encodes one of the two major oncoproteins of BPV-1. In this study, we demonstrate an interaction between the BPV-1 E6 protein and AP-1, the TGN (trans-Golgi network)-specific clathrin adaptor complex. AP-1 is a four-subunit protein complex required for clathrin-mediated cellular transport from the TGN. The AP-1/E6 interaction was observed in vitro and in cells. The E6 binding site on AP-1 was mapped to the N-terminal trunk domain of the gamma subunit. BPV-1 E6 preferentially associated with membrane-bound AP-1 in cells but not with free cytosolic AP-1. BPV-1 E6 was further shown to be recruited to isolated Golgi membranes and to copurify with clathrin-coated vesicles. The recruitment of BPV-1 E6 to Golgi membranes was AP-1 independent, but the E6 interaction with AP-1 was required for its association with clathrin-coated vesicles. Furthermore, AP-1 proteins could compete with BPV-1 E6 for binding to Golgi membranes, suggesting that the recruitment of BPV-1 E6 and AP-1 to Golgi membranes involves a common factor. Taken together, our results suggest that cytosolic BPV-1 E6 is first recruited to the TGN, where it is then recognized by membrane-bound AP-1 and subsequently recruited into TGN-derived clathrin-coated vesicles. We propose that BPV-1 E6, through its interaction with AP-1, can affect cellular processes involving clathrin-mediated trafficking pathway.

Adaptor Protein Complex alpha Subunits↗
PubMed1998

[Applied anatomy of the temporal and frontal regions in endoscopic temporal lifting].

OBJECTIVE: This anatomic study was carried out in a bid to decrease damage of the temporal branch of the face nerve in endoscopic temporal lifting. METHODS: We dissected the frontal-temporal region and located the temporal branch on 36 sides of adult head specimens. RESULTS: It was found that the temporal branch is deep to the temporoparietal fascia and frontal muscle. The temporal branch has one to four branches in general. The first one is 8.1 +/- 2.1 mm anterior to articular tubercle and 33.8 +/- 4.9 mm superior to the bony lateral canthus. The temporal branches locate below a line drawn from the articular tubercle to 40 mm above the bony lateral canthus. CONCLUSION: It is suggested that the operation incisions in the temporal region be selected above this line.

Adult↗
PubMed1998

[Expression of endothelial nitric oxide synthase gene in placental villus of preeclampsia].

OBJECTIVE: To investigate the expression of endothelia nitric oxide synthase (eNOS) mRNA in the villus of preeclampsia and the relationship between eNOS and preeclampsia. METHODS: Dot blot, using DIG-labeled human eNOS cDNA probe, had been used to examine the expression of eNOS gene in placental tissues of 9 normotensive pregnancy and 9 preeclampsia women. By using Leica QWIN image disposal and analysis system Mean OD of every dot was assessed. RESULTS: The level of eNOS mRNA in placental villus was significantly lower in preeclampsia woman than that of control group (P < 0.001). CONCLUSION: The decrease of eNOS in placental villus of preeclampsia may be one of the causes for human placental dysfunction and high impedance of fetoplacental circulation in preeclampsia. It may play an improtant role in the genesis of pregnancy induced hypertension.

Adult↗
PubMed1997

The bovine papillomavirus E6 protein binds to the LD motif repeats of paxillin and blocks its interaction with vinculin and the focal adhesion kinase.

The bovine papillomavirus type 1 (BPV-1) E6 oncoprotein can transform fibroblasts and induce anchorage-independent growth and disassembly of the actin stress fibers. We have previously shown that the E6 protein interacts with the focal adhesion protein, paxillin, suggesting a direct role of E6 in the disruption of the actin cytoskeleton. We have now mapped the E6 binding sites on paxillin to the LD motif repeats region, which has been implicated in mediating paxillin binding to two other focal adhesion proteins, vinculin and the focal adhesion kinase. The five LD motif repeats identified in paxillin do not contribute equally to its interaction with E6. The first LD repeat is most critical for paxillin binding to E6 both in vitro and in vivo. Furthermore, the binding of recombinant wild-type E6 protein to paxillin blocked the interaction of several cellular proteins with paxillin, including vinculin and the focal adhesion kinase. A mutant E6 protein (H105) which does not bind to paxillin had no effect on the binding of these cellular proteins to paxillin. These data suggest that E6 disruption of the actin stress fibers occurs through blocking the interaction of paxillin with its cellular effectors such as vinculin and the focal adhesion kinase.

Amino Acid Sequence↗