Biomedical subjects

G Chen

Publications and source records attributed to G Chen.

At least 703 records · Page 39Linked to original sources

PubMed1995

Enhanced adeno-associated virus vector expression by adenovirus protein-cationic liposome complex. A novel and high efficient way to introduce foreign DNA into endothelial cells.

Adeno-associated virus vector (AAV), a non-pathogenic integrating vector, can integrate on chromosome 19 in humans. But its gene transfer efficiency is quite low. In this study we combined adenovirus (Adv-5) capsid protein or the Fiber protein of Adv with liposome, termed adenosome (adenovirus protein-cationic liposome complex). This complex can bring AAV/CMV-LacZ to the endothelial cells, and improve the efficiency of gene transfer. It may be a novel, specific, stable and safe gene delivery system and will be widely used in human gene therapy.

Adenoviruses, Human↗

PubMed1995

Adenovirus mediated gene transfer of vascular smooth muscle cells and endothelial cells in vitro.

Introducing foreign gene(s) into vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) is the pre-requirement of gene therapy for cardiovascular diseases. We have explored the use of adenoviral vectors (Adv-CMV/LacZ) to transfer LacZ gene into cultured VSMCs and ECs. Our results demonstrated that adenoviral vectors transferred foreign gene into VSMCs and ECs high-efficiently with dose-dependent response pattern. The frequencies of transfection reached 100% at the viral titer of 10(9) pfu/ml. Comparing the sensitivities of VSMCs and ECs to adenoviral vectors, we found that ECs were more sensitive than VSMCs, of which the frequencies of transfection in ECs reached 80% while in VSMCs only 40% for 8 hrs after transfection. In addition, the transfection of ECs and VSMCs with adenoviral vectors was partly blocked by monoclonal antibodies to Fiber and Core protein of the adenoviral capsid, but not by monoclonal antibody to Hexon protein. It is suggested transfection of ECs and VSMCs with adenovirus vectors is mediated by Fiber or Core protein of adenoviral capsid proteins.

Adenoviruses, Human↗

PubMed1995

Complete reversal by thaliblastine of 490-fold adriamycin resistance in multidrug-resistant (MDR) human breast cancer cells. Evidence that multiple biochemical changes in MDR cells need not correspond to multiple functional determinants for drug resistance.

The emergence of drug resistance is a major obstacle to effective cancer chemotherapy. The identification of novel agents that serve as selective, potent and nontoxic modulators of drug resistance is thus an important goal for improving the success of cancer treatment. Thaliblastine (TBL), a plant alkaloid and P-glycoprotein (P-gp) inhibitor, is presently shown to fully reverse 490-fold resistance to Adriamycin (AdR) in a multidrug-resistant (MDR) human breast cancer cell line (MCF/AdR) that overexpresses P-gp, whereas the same treatment had no effect on AdR cytotoxicity in the drug-sensitive parental MCF-7 cells. Mechanistic studies showed that this striking resistance reversal was achieved without alteration of cellular levels of glutathione and without inhibition of glutathione S-transferase, glutathione peroxidase or P450 reductase by TBL, each of which is significantly altered in MCF/AdR cells, and each of which has been proposed to contribute to AdR resistance in this MDR line. Rather, resistance reversal by TBL can be entirely explained by this drug's capacity to restore the intracellular accumulation of AdR in the resistant cells. These results establish that MDR associated with P-gp overexpression can be fully reversed by the potent P-gp inhibitor TBL. They further indicate that although changes in multiple drug-metabolizing enzymes may accompany the development of MDR, these multiple biochemical alterations need not correspond to multiple functional determinants for drug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1995

[Double embolization of bronchial artery to control massive hemoptysis].

Bronchial arteriography and double embolization is to block the peripheral bronches of the bronchial artery with micro-gelatin particles and then the trunk of the artery with sponge gelatin. The blood flow from the artery trunk and from the rich arterial bronches which forms B-P bypass is blocked. By this way the embolization is more complete. Clinical observation of 93 cases shows that the success rate reached 91% which indicate that the massive hemoptysis could stopped by this method.

Adult↗

PubMed1995

Modulation of thiotepa antitumor activity in vivo by alteration of liver cytochrome P450-catalyzed drug metabolism.

The anticancer drug and alkylating agent thiotepa is metabolized by oxidative desulfuration to yield the alkylating metabolite N,N',N"-triethylenephosphoramide (TEPA) in a reaction that is catalyzed by specific liver cytochrome P450 (CYP) enzymes, including CYP2B1, the major phenobarbital-inducible P450 of rat liver, and CYP2C11, a constitutively expressed, male-specific form. The present study investigates the potential for modulating the cytotoxicity and antitumor activity of thiotepa by prior treatment of tumor-bearing rats with the CYP2B1 inducer phenobarbital or the CYP2C11 inhibitor 2-diethylaminoethyl-2,2-diphenylvalerate hydrochloride (SKF-525A) and examines the role of TEPA in the cytotoxicity of thiotepa in vivo. Administration of thiotepa to adult male rats bearing 9L gliosarcoma, grown s.c., resulted in dose-dependent cytotoxicity (ED90 approximately 12 mg/kg i.v., single dose), as determined by a tumor excision/in vitro colony formation assay carried out 24 hr after drug treatment. Tumor growth delay experiments revealed that thiotepa (5 mg/kg) inhibited 9L tumor growth over a 5- to 7-day period after alkylating agent treatment and this effect was accompanied by moderate body weight loss. Pretreatment with phenobarbital, under conditions in which liver CYP2B1 levels and liver microsomal thiotepa desulfuration to yield TEPA are both markedly increased, did not alter thiotepa's short-term (24-hr) cytotoxicity, as judged by a tumor excision assay, nor did it affect the extent of bone marrow toxicity associated with drug treatment. However, phenobarbital did block the tumor growth delay effect of thiotepa and it also attenuated the body weight loss that occurred during the first 5 days after drug treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

[NONMEM approach for estimating population pharmacokinetic parameters of phenytoin in Chinese epileptics].

Routine clinical pharmacokinetic data collected from epileptic out-patients who received phenytoin (PHT) were analysed to estimate population pharmacokinetic parameters. There were 258 steady-state serum phenytoin concentrations and associated dosage (mg.d-1) from 161 out-patients. The data were analysed using NONMEM program. The influence of body weight, drug combinations and sex on the maximum elimination rate (Vm) and age on the Michaelis-Menten constant (Km) were investigated. The Vm and Km of phenytoin in a 60 kg adult out-patient, without combination with other drugs (phenobarbital, clonazepam or diazepam) were estimated to be 439 mg.d-1 and 6.21 micrograms.ml-1, respectively. The best function adjusts Vm to the 0.57 power in proportion to body weight. The Km for patients less than 15 years old was 7% less than that for adults. The Vm of patients treated with phenytoin combined with phenobarbital, clonazepam or diazepam will increase 8.4 mg.d-1.

Adolescent↗

PubMed1995

[Influence of radiotherapy and chemotherapy on the function of malignant tumor patients and regulation function of acupuncture].

The observation on the indexes of cortisol, estradiol, estriol and testosterone showed that incretory function of malignant tumor patients had different extent of pathologic changes, after radiotherapy and chemotherapy, making the change strengthened. Acupuncture can regularize this disorder of incretory function of patients treated with radiotherapy and chemotherapy to some extent.

Acupuncture Therapy↗

PubMed1995

[Studies on diagnostic bacteriophage of Vibrio fluvialis].

Species of Vibrio fluvialis are identified by their biochemical characteristics so far, with a lot of items to be determined, overelaborate procedure and expensiveness. Inaccordance with the fact that bacteriophage is a specific parasite inhabited in bacteria and has been used in identifying other bacteria with high specificity, some of Vibrio fluvialis bacteriophage isolated from natural environment were selected to make diagnostic preparation for Vibrio fluvialis identification. Diagnostic positivity of Vibrio fluvialis averaged 84.27%, and 87.84% for those of human source. Cross-lysis rates both for the same Vibrio genus and that of different families in the same genus were less then 3%, and no cross-lysis was found for the other enteric bacteria in different genera. There was no significant difference between diagnostic bacteriophage and biochemical tests for Vibrio of unknown species. This method was highly specific, sensitive, rapid, simple and inexpensive, and could be used in diagnosis of Vibrio fluvialis.

Bacteriophages↗

PubMed1995

[Evaluation of population pharmacokinetics of cyclosporin A in renal transplantation patients with NONMEM].

NONMEM program was applied for estimating population pharmacokinetic parameters of cyclosporin A (CsA). The influence of body weight, age, sex and drug administration history on clearance were investigated. There were 281 CsA concentrations in whole blood from 60 clinical renal transplantation patients. Samples were analysed by HPLC and FPIA (TDx, Abbott, monoclonal antibody). One compartment open model with first-order absorption and elimination was used to analyse the data. Population mean values of CL(L.h-1), Vd(L), and Ka(h-1) were 59.8, 227, and 1.28 respectively. The interindividual variations of CL, Vd, and Ka were 30.27%, 29.01%, and 75.10% respectively. The residual error was 31.19%. The adjustment value of weight to clearance was 0.03 times with additional model. CL increased 4.31 in male patients, and decreased 12.7 when patients were treated with CsA for a long time.

Adult↗

PubMed1995

Pharmacologic profile of natural products used to treat psychotic illnesses.

Natural products have a long history of being the sources for therapeutic drugs in medicine. Investigations of natural products also have the potential for enhancing our understanding about the pathophysiology and treatment of various disorders. The screening assays described here were conducted on the phytochemical and pharmacological profiles of natural products used to treat psychotic illnesses in Korean traditional medicine, which are eligibly archived in Tongeuibogam, a traditional medicinal book in Korea. Two rounds of radioligand receptor binding assays on natural products demonstrated that many plants show potent selectivity to various receptors, especially monoamine receptors presumed to be involved in mental disorders. Further studies for the pharmacologic activity of active ingredients and in vivo behavioral profiles focusing on the central nervous system (CNS) effects are currently under way with these plant extracts. These investigations may lead to the development of new psychotropic drugs with no serious side effects, a major concern for modern psychopharmacology.

Animals↗

PubMed1995

Effect of warm ischemic injury on morphology and viability of aortic valves in rats.

Warm ischemia is one of the most important causes of valvular damage from death of donor to its valve harvesting. This study aimed at using qualitative and quantitative methods to characterize warm ischemic injury through models of SD rat's aortic valves and design to show the relationship among ultrastructural, biological and biochemical changes concerning with the length of warm ischemia time (WIT). 102 harvested SD rat's aortic valves were divided into 6 groups of different ischemic time for this study. 432 photomicrographs of transmission electron microscopy (TEM) were put into computer for analysis. The volume ratio of nucleus to plasma in cells (Vnp) and the ratio of extramembrane area to volume of mitochondria (S/V) were used to characterize the degree of valvular cell injuries. Valvular cells culture and biochemical metabolism including glucose degradation and 3H-TdR absorption rate were adopted. The valvular cells depicted a significant decrease and 3H-TdR taking-up also being inhibited under the influence of prolonged WIT.

Animals↗

PubMed1995

[Studies on amino acid and chemical element in five species of filariae].

Five species of human and domestic animal filariae (B. m, S. d, S. l, S. e, D. i) after lyophilization and hydrolysis were resolved using HPLC and type WFX-IB AAS to determine amino acid (AA) and microelement (ME) content, respectively. The results showed that there were 16 and 17 AA in B. malayi and the animal filariae, respectively. Among AA, the total amount (microgram/mg dry wt.) was markedly higher in animal filariae than that in B. malayi in which the content of acidic and aliphatic AA was significantly higher than those of basic and aromatic AA, respectively. Among five ME (Zn, Cu, Fe, Mn, Cd) and two microelements (Ca, Mg) found in all these filariae. Zn Content was the predominant ME and Ca was much more than Mg.

Amino Acids↗

PubMed1995

[Inhibition of glutamate uptake in rat brain synaptosome by pyrethroids].

In vitro studies showed deltamethrin (1 x 10(-7)-1 x 10(-4) mol/L) could inhibit 3H-DL-glutamate uptake in rat cerebral cortex and hippocampus synaptosome by 7.2%-21.5% and 10.4%-25.1%, respectively, with a dose-response pattern. But only in high-dose permethrin (1 x 10(-4) mol/L) can significantly reduce 3H-DL-glutamate uptake in rat hippocampus synaptosome. In addition, deltamethrin also can reduce 3H-DL-glutamate uptake in cerebellum and striatum of rats by 16.5% and 31.8%, respectively. It is suggested that both deltamethrin and permethrin, especially the former, can disturb the function of brain tissue in high-affinity-glutamate uptake with their alpha-cyano-group. So pyrethroids could play an important role in cerebral stimulation in mammals.

Animals↗

PubMed1995

[Hepatitis B virus, the main cause of membranous nephropathy in China].

To investigate the role of hepatitis B virus in the pathogenesis of membranous nephropathy (MN) in China, we studied 67 MN patients (excluding lupas nephritis V) with immunoperoxidase technique. In 46 (68.2%) of the 67 MN patients, HBV antigens (HBsAg, HBcAg and HBeAg) were detected in their glomeruli, and HBsAg, the dominant antigen was detected in 45 patients (67.2%). HBV-Ag was detected less frequently in the older MN group (33.3%) (> 50 years old) than in the two younger MN groups (73.1%, 75%) (< 30 years old, 30-50 years old) (P < 0.05). 30 randomly selected MsPGN patients were studied as controls. HBV antigens were detected in only 3 out of the 30 MsPGN patients. The HBV antigen positivity rate of the MN group was significantly higher than that of the MsPGN group (P < 0.01). The results suggested that HBV may be the main cause of MN in China, especially in those younger than 50 years, but not of MsPGN. HBsAg containing immune complexs (IC) may play an important role in the pathogenesis of HBV-MN.

Adolescent↗

PubMed1995

[The morphologic changes of endometrial hematostatic reaction in intrauterine devices induced menorrhagia].

OBJECTIVE: To investigate the relationship between intrauterine contraceptive devices (IUD) induced menorrhagia and endometrial spiral arteriolar contractive function and endometrial superficial vessels thrombus formation function. METHODS: Sixty five subjects were admitted and divided into IUD bleeding group (25 cases), IUD non-bleeding group (20 cases) and IUD non-user group (20 cases). The samples were obtained by curettage within 24 hours prior to menstruation and observed under light and electron microscope. The morphologic changes of endometrial micro-vessels, spiral arterioles were observed and diameter of spiral arterioles were measured. RESULTS: Compared with IUD non-user group, the degenerative changes of spiral arteriolar wall were more severe and the dilatation of spiral arteriolar lumen was obvious especially in spongious layer. In IUD non-bleeding group, these changes were mild. The platelet and fibrin thrombus count was the highest in IUD non-bleeding group and the lowest in IUD bleeding group. CONCLUSIONS: These results suggested that IUD induced menorrhagia might correlated with poor contraction of spiral arterolars in spongious layer and poor thrombus formation. Mild degeneration and dilatation of spiral arterioles and a lot of thrombus were seen in IUD non-bleeding group, and this might be the cause that the mentrual blood loss in this group did not increase obviously.

Adult↗

PubMed1995

A study on oliguric standard in the elderly.

Water deprivation test was done in 44 healthy elderly persons, 26 were male, and 18 were female. They were deprived of the intake of water for 25 hours. The results showed that the maximal renal concentration function both in the elderly males and females was 887 +/- 91 mmol/L and 888 +/- 127 mmol/L respectively. The renal excretion of waste products in 24 hours both in the elderly males and females was 815 + 170 mmol/d and 620 + 132 mmol/d respectively. On the basis of point estimation, the minimal essential urine volume per day in the elderly males and females was 926 ml/d and 708 ml/d respectively, if the daily urine volume of the elderly is less than this level, then, the metabolic products generated per day can not be excreted by the kidney, and it would result in disorders of internal environment. Therefore, the oliguric standard in elderly males and females must be less than 926 ml/d and 708 ml per day respectively.

Age Factors↗

PubMed1995

[Colorimetric method for the determination of carboxymethyl pachyman].

Carboxymethyl pachyman gives a red color when treated with phenol and concentrated sulfuric acid. The reaction is sensitive and the color is stable. Based on this reaction, a colorimetric method has been developed to analyse carboxymethyl pachyman, and some factors that affect the determination were discussed.

Adjuvants, Immunologic↗

PubMed1995

Enzyme- and sex-specific differences in the intralobular localizations and distributions of aryl sulfotransferase IV (tyrosine-ester sulfotransferase) and alcohol (hydroxysteroid) sulfotransferase a in rat liver.

Aryl sulfotransferase (AST) IV and alcohol (hydroxysteroid) sulfotransferase a (STa) catalyze the formation of sulfuric acid esters from a diverse array of xenobiotic and endogenous molecules in the liver. Despite the fact that many studies have addressed the metabolic importance and catalytic characteristics of these two sulfotransferases, relatively little is known about their comparative in situ localizations and intralobular distributions in liver. The present investigation utilized specific rabbit antisera prepared against AST IV and STa for immunoperoxidase staining of serial sections from livers of male and female Sprague-Dawley rats and computer-assisted image analysis of immunohistochemical staining intensity by means of microdensitometry. The overall concentration of AST IV was greater in males than in females, although the intralobular distribution of the enzyme was similar in the livers of both male and female rats, wherein centrilobular hepatocytes contained a greater level of AST IV than did midzonal cells, and midzonal hepatocytes had a greater concentration of AST IV than did periportal hepatocytes. In marked contrast, STa was present in livers of female rats at a much greater overall concentration than in livers of male rats. Furthermore, whereas the intralobular distribution of the enzyme was similar in both males and females, STa was present at greater concentrations in periportal hepatocytes than in midzonal hepatocytes and at greater concentrations in midzonal cells than in centrilobular hepatocytes. Significant intrazonal heterogeneity in STa levels within hepatocytes was also observed, particularly in livers of female rats. These results indicate that, whereas the overall hepatic concentrations of these enzymes are clearly sex-dependent, the intralobular distributions of AST IV and STa are characteristic of each particular sulfotransferase.

Amino Acid Sequence↗