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Biomedical subjects

Li-Xin Chen

Publications and source records attributed to Li-Xin Chen.

14 recordsLinked to original sources

Fiber-optic sensor for iodine based on a covalently immobilized aminobenzanthrone Schiff base.

An aminobenzanthrone Schiff base has been synthesized as a new fluorescence carrier for the preparation of an optical chemical sensor for iodine. The response of the sensor is based on fluorescence quenching of the aminobenzanthrone Schiff base by iodine. The sensor shows a linear response toward iodine in the range of 1.0 x 10(-5) to 1.0 x 10(-3) mol l(-1), with a detection limit of 6.0 x 10(-6) mol l(-1) at pH 8.0. Leaching of the fluorophore from the membrane is effectively hindered by covalent immobilization, resulting in an enhanced sensor lifetime. In addition to satisfactory reproducibility and reversibility, the prepared sensor exhibits sufficient selectivity toward iodine with respect to other coexisting ions. The sensor has been applied to the determination of iodine in common salt samples.

Anthracenes↗

[Primary investigation of dose-effect relationship of 153Sm-EDTMP in treating multiple bone metastases].

BACKGROUND & OBJECTIVE: Dose calculation of radionuclide internal irradiation is a hot topic and difficulty of nuclear medical researches. This study was to calculate the focus absorption dose of 153Sm-EDTMP with the Monte Carlo EGS4 method for treatment of bone metastases from nasopharyngeal carcinoma or breast cancer, and investigate the relationship between the focus absorption dose and painkilling effect of 153Sm-EDTMP. METHODS: Four patients with multiple bone metastases from nasopharyngeal or breast carcinoma and suffered from grade IV bone pain were treated with radionuclide internal irradiation of 153Sm-EDTMP. The absorption dose and dose distribution of bone metastases and other targeted organs were calculated with MC EGS4 program based on the time-order SPECT/CT scanning and the measurement of the radioactivity in the urine accumulation. The release of bone pain and the improvement of life quality were observed. RESULTS: Bone pain of the patients was significantly alleviated to grade II for 3-4 weeks after internal 153Sm-EDTMP irradiation. The 3-dimensional absorption dose distribution image of bone metastases and targeted organs showed that the dose distribution in bone metastases was not asymmetrical. After injection of 0.65x37 MBq/kg 153Sm-EDTMP, the highest absorption dose in bone lesions was about 4.9-5.9 Gy, and the dose in the lesion margin was about 2.0 Gy. Use the highest dose as reference dose point, the relative absorption dose values of bone marrow, bone cortex, and soft tissue near lesions were 0.48-1.1 Gy, 0.51-0.85 Gy, and 0.01-0.14 Gy, respectively. CONCLUSIONS: The absorption dose of bone metastases is significantly lower than treatment dose of 30 Gy after single irradiation of 153Sm-EDTMP. The painkilling effect is limited and in accordance with clinical observation.

Adult↗

[Three-dimensional dose calculation of 153Sm-EDTMP in treating bone metastasis--comparison of Monte Carlo and S value calculation methods].

BACKGROUND & OBJECTIVE: Three-dimensional (3D) dose calculation of radionuclide therapy for specified patients is a research interest in nuclear medicine, of which the main methods include S value calculation method, dose point kernel calculation method, and Monte Carlo (MC) simulation method. This study was to compare 3D absorbed dose calculation of 153Sm-EDTMP in treating a specified patient with bone metastasis between MC and S value methods. METHODS: A 3D dose calculation program was built based on the MC program EGS4, and the S value of nuclide 153Sm was calculated. For the specified patient with bone metastasis, 153Sm activity in excreted urine was measured at 0, 0.5, 2, 3.5, 5 and 6 h after injection of 153Sm-EDTMP. The accumulative activity is calculated by fitting measurement data. Based on the fusion SPECT/CT images of the patient, 3D absorbed dose is calculated by MC and S value methods. RESULTS: The iso-dose distribution curves of MC and S value calculation results were similar, and the dose was mainly collected in the bone. According to the 2 methods, the maximum doses were 3.92 Gy and 3.71 Gy with a difference of 5%. On the dose-volume histogram of the calculation volume, D10 (the highest dose of the 10% volume) were 2.14 Gy and 2.00 Gy with a difference of 7%; D20 (the highest dose of the 20% volume) were 0.58 Gy and 0.51 Gy with a difference of 14%. In general, the data of S value calculation were smaller than the data of MC calculation. CONCLUSIONS: MC and S value could be used to calculate the 3D dose of radionuclide therapy based on nuclear medical image. S value is a fast and simple method for the dose evaluation although the error of the calculation is relatively bigger.

Bone Neoplasms↗

[Background chloride currents in fetal human nasopharyngeal epithelial cells].

To characterize the background current in fetal human nasopharyngeal epithelial cells and clarify its relationship with volume activated Cl(-) currents (I(Cl,vol)), whole-cell patch clamp and cell imaging techniques were employed. Under isotonic conditions, a background current [(5.9+/-2.1) pA/pF at +80 mV, n=21] was detected. The current presented a weak outward rectification and a negligible time-dependent inactivation. The current-voltage relationship showed that the reversal potential of the background current [(-0.73+/-1.7) mV, n=21] was close to the calculated equilibrium potential for Cl(-)(-0.9 mV). Application of extracellular hypertonic stimulation (440 mOsmol/L) suppressed the current by (59.6+/-7.1)% and the inhibition was reversible after returned to isotonic conditions. Bathing the cells in hypotonic solution (160 mOsmol/L) induced a volume-sensitive Cl(-) current. The Cl(-) channel blockers, tamoxifen (20 micromol/L) and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) (100 micromol/L), inhibited the background current by (74.0+/-5.2)% (P<0.01, n=5) and (60.9+/-8.9)% (P<0.01, n=6) at +80 mV and increased basal cell volume by (107.7+/-2.9)% (P<0.01, n=25) and (104.4+/-2.4)% (P<0.01, n=19), respectively. The data indicate that Cl(-) current is an important component of the background current in fetal human nasopharyngeal epithelial cells. The background Cl(-) current is involved in volume activated Cl(-) current and basal cell volume regulation.

Cells, Cultured↗

Activation of chloride current and decrease of cell volume by ATP in nasopharyngeal carcinoma cells.

Whole-cell patch clamp and cell volume measurement techniques were used to investigate the ATP-activated chloride current and the ATP effect on cell volume in nasopharyngeal carcinoma cells. Extracellular application of ATP in micromolar concentrations activated a current with the properties of modest outward rectification and negligible time-dependent inactivation in a dose-dependent manner. The current reversed at a potential [(-0.05+/-0.03) mV] close to the Cl- equilibrium potential (-0.9 mV). Substitution of Cl- with gluconate in the extracellular solution decreased the ATP-activated current and shifted the reversal potential positively. NPPB, one of the chloride channel blockers, inhibited the current by (81.03+/-9.36)%. The current was also depressed by the P2Y purinoceptor antagonist, reactive blue 2, by (67.39+/-5.06)%. ATP (50 micromol/L) decreased the cell volume under the isotonic condition. Depletion of extracellular and intracellular Cl- abolished the ATP effect on cell volume. The results suggest that extracellular ATP of micromolar scales can induce a chloride current associated with cell volume regulation by activation of chloride channel through binding to purinoceptor P2Y.

Adenosine Triphosphate↗

Volume-activated Cl- current in migrated nasopharyngeal carcinoma cells.

The transwell chamber migration assay and the patch-clamp technique were used to investigate the volume-activated Cl(-) current (I(Cl.vol)) in migrated nasopharyngeal carcinoma cells (CNE-2Z). 47% hypotonic solution activated a ICl.vol in the migrated CNE-2Z cells. Compared with the control cells (non-migrated), the properties of this current and the sensitivity to Cl(-) channel blockers were changed. The current density in migrated CNE-2Z cells was higher than that in non-migrated cells. The current was almost completely inhibited by extracellular application of adenosine-5'-triphosphate (ATP, 10 mmol/L), 5-nitro-2-3-phenylpropylamino benzoic acid (NPPB, 100 mmol/L) and tamoxifen (30 mmol/L) in all voltage steps applied. The inhibition of NPPB and tamoxifen on the current was stronger in migrated cells than that in non-migrated cells. The permeability sequence of the four anions was Br(-)>Cl(-)> I (-)>Gluconate. The sequence was different from that of the non-migrated cells (I(-)> Br(-)> Cl(-)> Gluconate). The results suggest that volume-activated chloride channels may be involved in the CNE-2Z cell migration.

Carcinoma↗

ClC-3 expression in the cell cycle of nasopharyngeal carcinoma cells.

The immunofluorescence approach, the confocal microscopy and the patch-clamp technique were used to investigate the expression of ClC-3 (one of the candidates of volume-activated chloride channels) and its relationships with the volume-activated chloride current and the capacity of regulatory volume decrease (RVD) in the cell cycle of nasopharyngeal carcinoma cells (CNE-2Z cells). The results indicated that CNE-2Z cells expressed ClC-3. ClC-3 was located predominantly inside the cells but not in the membrane. Both the expression level and the distribution of ClC-3 were cell cycle dependent. ClC-3 expression was low in G1 but high in S phase. The cells in G2/M phase possessed an intermediate level of the expression. ClC-3 expression level was negatively correlated to the RVD capacity and amplitude of the volume-activated chloride current in the cell cycle. The results suggest that ClC-3 may be an important factor in the regulation of cell cycle progression, but that it is probably not the chloride channel associated with RVD in these cancer cells.

Adenosine Triphosphate↗

Experimental study of quantitative assessment of left ventricular mass with contrast enhanced real-time three-dimensional echocardiography.

OBJECTIVES: To evaluate the feasibility and accuracy of measurement of left ventricular mass with intravenous contrast enhanced real-time three-dimensional (RT3D) echocardiography in the experimental setting. METHODS: RT3D echocardiography was performed in 13 open-chest mongrel dogs before and after intravenous infusion of a perfluorocarbon contrast agent. Left ventricular myocardium volume was measured according to the apical four-plane method provided by TomTec 4D cardio-View RT1.0 software, then the left ventricular mass was calculated as the myocardial volume multiplied by the relative density of myocardium. Correlative analysis and paired t-test were performed between left ventricular mass obtained from RT3D echocardiography and the anatomic measurements. RESULTS: Anatomic measurement of total left ventricular mass was 55.6 +/- 9.3 g, whereas RT3D echocardiographic calculation of left ventricular mass before and after intravenous perfluorocarbon contrast agent was 57.5 +/- 11.4 and 55.5 +/- 9.3 g, respectively. A significant correlation was observed between the RT3D echocardiographic estimates of total left ventricular mass and the corresponding anatomic measurements (r = 0.95). A strong correlation was found between RT3D echocardiographic estimates of left ventricular mass with perfluorocarbon contrast and the anatomic results (r = 0.99). Analysis of intraobserver and interobserver variability showed strong indexes of agreement in the measurement of left ventricular mass with pre and post-contrast RT3D echocardiography. CONCLUSIONS: Measurements of left ventricular mass derived from RT3D echocardiography with and without intravenous contrast showed a significant correlation with the anatomic results. Contrast enhanced RT3D echocardiography permitted better visualization of the endocardial border, which would provide a more accurate and reliable means of determining left ventricular myocardial mass in the experimental setting.

Animals↗

[Analysis of target localization errors in fractionated stereotactic radiotherapy for head and neck carcinoma].

BACKGROUND & OBJECTIVE: Accurate target localization is the essential requirement in the quality control in fractionated stereotactic radiotherapy (FSRT). This paper is to analyze the magnitude of errors in FSRT for head and neck carcinoma including the errors of CT localization, mechanical isocenter, setup of patients, and CT image. METHODS: The stereotactic radiotherapy treatment planning system (SRT-TPS), target simulator and head frame were used to check the errors of target localization during each radiation procedure. Five reference points were set randomly; the CT localization error was measured using the target simulator. Seven different mechanical angles of Gantry/Table were selected; the magnitude of isocentric errors of Philips SL-18 linear accelerator were acquired with films. Setup errors were collected by portal films. The image error possibly from CT image artifact was analyzed after scanning a self-made phantom by CT. RESULTS: The CT localization error was(1.5+/-0.4)mm. The maximal error of the mechanical isocenter was (1.0+/-0.6)mm according to the different mechanical gantry/table angles. The distance error of patient setup was (1.0+/-0.3)mm. The maximal total errors estimate was (2.1+/-0.8)mm. CONCLUSIONS: The effect of target localization of every procedure should be taken in account in FSRT, the results of the error analysis can be used to determinate the planning target volume in the treatment.

Dose Fractionation, Radiation↗

[Clinical study on treating insulin resistance and promoting ovulation in polycystic ovary syndrome].

OBJECTIVE: To investigate the effects of metformin and clomiphene on infertility caused by polycystic ovary syndrome (PCOS) with insulin-resistance (IR) and to observe the effects of metformin on PCOS with pseudoacanthosis nigricans (AN) and IR. METHODS: Seventy infertility patients caused by PCOS with IR were randomly divided into three groups : patients in group Aa (n = 20) took metformin 500 mg only, three times daily for 3 months; patients in group Ab (n = 20) took clomiphene 50 mg only, once daily from the 5th day of menstrual cycle or withdrawal bleeding for 5 days and 3 cycles, and patients in group Ac (n = 30) were treated by metformin and clomiphene for 3 cycles, with the same dosages as groups Aa and Ab. Thirty patients who suffered from PCOS with AN and IR were served as group B, They took metformin only, the same as group Aa. The following indexes were measured before and after three months or cycles of treatment in all the patients: body height, weight, waistline, hipline, body mass index (BMI), waist hip ratio (WHR), fasting insulin (FINS), fasting blood-glucose (FBG), total cholesterol (TC), triglyceride (TG), and sex hormones [follicle-stimulating hormone (FSH), luteotropic hormone (LH), prolactin (PRL), estradiol (E(2)), progestin (P), testosterone (T)]. RESULTS: The pregnant rate was 15% (group Aa), 20% (group Ab), and 57% (group Ac) respectively. It was significantly higher in group Ac than in groups Aa and Ab, (P < 0.01), while there was no significant difference between the latter two groups (P > 0.05). In group Ac the pretreatment levels of FINS, BMI, T, TG, and TC were (49.7 +/- 6.4) mU/L, 29.4 +/- 2.2, (6.4 +/- 2.2) nmol/L, (4.1 +/- 1.0) mmol/L, (6.3 +/- 0.5) mmol/L, and posttreatment levels were (27.7 +/- 1.8) mU/L, 23.6 +/- 5.2, (3.8 +/- 2.0) nmol/L, (2.2 +/- 0.7) mmol/L, (4.6 +/- 0.5) mmol/L. In group Aa pretreatment levels of FINS, BMI, T, TG, and TC were (50.0 +/- 8.2) mU/L, 28.7 +/- 1.2, (6.4 +/- 2.0) nmol/L, (4.3 +/- 1.2) mmol/L, (6.6 +/- 0.3) mmol/L, and posttreatment levels were (29.9 +/- 8.2) mU/L, 22.4 +/- 9.3, (4.3 +/- 0.9) nmol/L, (2.3 +/- 0.3) mmol/L, (4.8 +/- 0.6) mmol/L. In group B pretreatment levels of FINS, BMI, T, TG, and TC were (51.0 +/- 8.1) mU/L, 29.8 +/- 3.1, (6.3 +/- 3.5) nmol/L, (4.5 +/- 1.2) mmol/L, (6.8 +/- 0.2) mmol/L, and posttreatment levels were (28.5 +/- 2.8) mU/L, 23.4 +/- 6.1, (3.0 +/- 0.9) nmol/L, (2.3 +/- 0.9) mmol/L, (5.0 +/- 0.6) mmol/L. In groups Ac, Aa and B, the IR condition was obviously improved and posttreatment serum levels of T, TG, TC, FINS and BMI were significantly lower than those of pretreatment (all P < 0.01). In group Ab pretreatment levels of FINS, BMI, T, TG, and TC were (48.8 +/- 7.4) mU/L, 27.3 +/- 2.8, (6.0 +/- 2.0) nmol/L, (3.9 +/- 1.4) mmol/L, (6.4 +/- 0.6) mmol/L, and posttreatment levels were (42.9 +/- 7.0) mU/L, 27.5 +/- 3.1, (4.0 +/- 2.4) nmol/L, (3.9 +/- 0.3) mmol/L, (5.9 +/- 0.3) mmol/L, (all P > 0.05). Among patients in group B, 90% (27/30) menstrual condition and ovulation function were improved and AN was reduced in different degree after three months' treatment. CONCLUSION: Metformin can increase the sensitivity of PCOS to clomiphene and improve ovulation function of clomiphene. Metformin plus clomiphene is an effective way of treating infertility caused by PCOS with IR.

Adult↗

Proton "off-on" behaviour of methylpiperazinyl derivative of naphthalimide: a pH sensor based on fluorescence enhancement.

In a search for new type pH sensing fluorophores, the possibility of using the proton "off-on" switch behaviour of naphthalimide derivatives for optical pH sensor preparation has been explored. A new compound, N-allyl-4-(4[prime or minute]-methyl-piperazinyl)-1,8-naphthalimide (AMPN), was synthesized. The enhancement of fluorescence of AMPN with the increase of hydrogen ion concentration is based on arresting photo-induced electron transfer to the naphthalimide fluorophore from aliphatic amine group after its protonation. The Stokes Shift of the proposed type of pH sensing fluorophore is significantly larger than that of the fluorescein counterparts. To avoid the leakage of the fluorophore, AMPN was photo-copolymerized with 2-hydroxyethyl methacrylate and acrylamide on the glass surface. The fluorescence intensity of membrane contacted with a pH 3.50 buffer is 4.7 times of that for pH 12.00 buffer solutions. The proposed pH sensor is not susceptible to ionic strength and shows good selectivity, repeatability and short response time. The membrane shows a good stability with a lifetime over two months. The sensor can be used for the determination of pH in the range of pH 4.5-9.0, without interference of most commonly co-existing inorganic ions and some organic species. The sensor has been applied to the analysis of urine samples.

Biosensing Techniques↗

A coumarin derivative covalently immobilized on sensing membrane as a fluorescent carrier for nitrofurazone.

A coumarin derivative 4-methyl-8-methylacrylamide-2H, 5H-pyrano [3, 2-C] benzpyran 2, 5-dione (MMPBD) has been synthesized as a fluorescent carrier for preparing an optical chemical sensor. The carrier is immobilized on a quartz glass plate surface treated with a silanizing agent to prevent the leakage of the dye. This MMPBD sensor can be utilized for a nitrofurazone (NF) assay based on fluorescence quenching. The sensor shows good repeatability, a long lifetime and a fast response of less then 50 s. NF can be determined in the range between 1.0x10(-6)-1.0x10(-3 )mol L(-1) with a detection limit of 8.0x10(-7) mol L(-1 )at pH 7.0.

Coumarins↗

Carbazole as fluorescence carrier for preparation of doxycycline sensor.

Carbazole is a promising pharmaceutical species. A novel optical sensor for determining doxycycline based on the fluorescence quenching of N-allylcarbazole immobilized on an quartz glass plate surface by covalent bonding has been described. The sensor shows satisfactory virtues in reversibility, repeatability, selectivity and sufficient lifetime resulting from its excellent optode membrane. Its response time is less than 60 s. The determination range and detection limit of the sensor are 6.0 x 10(-7)-2.0 x 10(-3) M and 2.0 x 10(-7) M, respectively. The lifetime of each sensor is at least three to four months. The sensor can be used for direct determination of doxycycline in pharmaceutical preparations and urine samples.

Animals↗

The role of MDR1 gene in volume-activated chloride currents in pigmented ciliary epithelial cells.

The role of multidrug resistance (MDR1) gene in the activation of volume-activated chloride currents in bovine pigmented ciliary epithelial (PCE) cells was investigated by the patch-clamp technique, the antisense approach, the immunofluorescent technique and the confocal microscopy. PCE cells express P-glycoprotein (P-gp, the product of MDR1 gene). An MDR1 antisense oligonucleotide suppressed MDR1 expression (93% reduction of P-gp immunofluorescence), delayed the activation of a volume-activated chloride current (latency prolonged by 109%), reduced the activation rate by 62% and decreased the peak value of the current by 56%. The transfection reagent lipofectin and the mismatch control oligonucleotide did not significantly affect the current. The data indicate that the volume-activated chloride current is associated with the endogenous expression of MDR1 gene in PCE cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗