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Biomedical subjects

X Tan

Publications and source records attributed to X Tan.

At least 55 records · Page 3Linked to original sources
PubMed2000

Carbon disulfide at a Chinese viscose factory external and internal exposure assessment.

This article presents the results of carbon disulfide exposure measurements in a Chinese viscose rayon factory. The objectives of the study were to identify the external exposure levels at a large factory and to investigate the 2-thiothiazolidine-4-carboxylic acid (TTCA) concentrations in the urine of the subjects who were exposed to carbon disulfide in the working place atmosphere. The metabolism of carbon disulfide in the exposed subjects was also studied in order to demonstrate the best points in time for the internal exposure sampling. The measurement of the amount of personal exposure to carbon disulfide in the air of the workplace was performed by GC-FPD; the presence of TTCA in the workers urine was analyzed by use of a modified HPLC method. The kinetics of TTCA excretion was studied by analyses at different time-points both during and after exposure to carbon disulfide in the subjects. A total of 155 personal samples were obtained. The carbon disulfide concentration in the staple viscose hall was 13.72 +/- 1.12 mg m-3 in terms of the geometric mean +/- geometric standard deviation, and was 20.05 +/- 1.33 mg m-3 in the filament spinning hall. The TTCA values in the subjects who worked in the staple spinning hall were 1.18 +/- 0.43 mg g-1 creatinine and 1.07 +/- 0.38 mg g-1 creatinine for subjects working in the filament spinning hall. The best time for TTCA sampling is at the end of the working shift, the TTCA excretion was stable for a period of 4-12 h after exposure of the subjects to the carbon disulfide. It might be that the Chinese have different anthropometric characteristics; a sampling bias may therefore appear among different races.

Adult↗
PubMed2000

Association of a functional polymorphism of the monoamine oxidase A gene promoter with personality and psychiatric symptoms.

A functional polymorphism in the promoter of the monoamine oxidase gene has recently been described by Sabol et al. This polymorphism is a strong candidate for associations with personality traits and psychiatric symptoms. We report relevant data from a general population sample of 850 Caucasian Australians. We found no associations with anxiety and depression symptoms, with personality traits that predispose to anxiety (neuroticism, behavioral inhibition, negative affect) or to a personality trait related to antisocial behavior (psychoticism).

Adult↗
PubMed2000

Pharmacokinetics of bis(t-butyl-SATE)-AZTMP, a bispivaloylthioethyl prodrug for intracellular delivery of zidovudine monophosphate, in mice.

The pharmacokinetics of a bispivaloylthioethyl prodrug of zidovudine monophosphate (AZTMP), bis(t-butyl-SATE)-AZTMP, and intracellular conversion of the prodrug to AZTMP were characterized following intravenous (i.v.) and oral (p.o.) administration of the prodrug to mice. Concentrations of bis(t-butyl-SATE)-AZTMP, AZTMP and zidovudine (AZT) in blood, red blood cells, plasma, brain and lymph nodes were determined by HPLC. Following i.v. administration of bis(t-butyl-SATE)-AZTMP, concentrations of the prodrug declined rapidly with low levels of the prodrug detected until 4 h. Both bis(t-butyl-SATE)-AZTMP and AZTMP were detected in brain 3 min after dosing. AZTMP was found in both plasma and peripheral red blood cells, peaking at approximately 30 min and remaining detectable until 2 h. No AZTMP was detected in lymph nodes. Compared to the pharmacokinetics of AZT following its i.v. administration, i.v. administration of bis(t-butyl-SATE)-AZTMP produced lower peak concentrations of AZT in plasma, peripheral red blood cells, brain and lymph nodes. However, terminal half-lives of AZT were significantly prolonged following administration of the prodrug. Following p.o. administration of bis(t-butyl-SATE)-AZTMP, neither the prodrug nor AZTMP were detectable in whole blood. The conversion of AZT from bis(t-butyl-SATE)-AZTMP in plasma and peripheral red blood cells following p.o administration was 12.1% of that following i.v. administration of the prodrug. Bis(t-butyl-SATE)-AZTMP demonstrated promising potential for intracellular delivery of AZTMP. The prodrug also prolonged the retention of AZT in mice, and particularly increased delivery of AZT to the lymphatic and central nervous systems.

Administration, Oral↗
PubMed2000

[Development of a control and monitor system for the cardiopulmonary cerebral resuscitation(CPCR) device].

A novel idea in developing cardiopulmonary-cerebral resuscition(CPCR) device has been developed, using a combination of membrane artificial lung(oxygenator), mild-hypothermia, and centrifugal blood pump technologies. A control system for the CPCR has been introduced, using converter control and sensor monitor, with 8031 chips as the controller. Pressure, flow rate and temperature monitors were installed in the system. Two modes of blood pump regulation have been adopted, i.e. continous flow and pulsatile flow. The in vitro evaluation tests showed that the two modes were reasonable and feasible.

Animals↗
PubMed2000

[Exploration on features of early medical activities of Miao nationality].

The Miao Minority medicine has a long history, and it originated thousands of years ago. The features of the Miao Minority medicine in the early age include all kinds of herbs which were very popular. Thus, a long-term "combination of witch and doctor" period existed in the early age of Miao Minority. This striking feature has great influence in the Miao Minority medicine, and this influence goes on until today. The Miao Minority doctors were good at external treatment in the early age. The above three points are worth studying, constituting the distinct traditional features of the Miao Minority medicine.

China↗
PubMed2000

[Effects of different catechins on cell cycle arrest and induction of apoptosis in LoVo cells].

OBJECTIVE: To investigate the effects of green tea (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin-3-gallate (ECG)and (-)-epicatechin (EC) on the cell cycle arrest and induction of apoptosis in human colon carcinoma LoVo cell line. METHODS: The cytotoxicity, cell cycle arrest and apoptosis-associated alterations in morphology and biochemistry were examined using the tetrazolium salt reduction (MTT) assay, gel electrophoresis, transmission electron microscope and flow cytometry after treatment of LoVo cells with the four catechins. RESULTS: Treatment of LoVo cells with EGCG and EGC resulted in the growth suppression and induction of apoptosis in a time- and concentration-dependent manner. ECG and EC, however, did not have the same effects. In addition, the four catechins had different effects on the cell cycle of LoVo cells. Treatment with EGCG, EGC and ECG caused LoVo cells arrest at G1 phase in the cell cycle progression, whereas EC resulted in an arrest at S phase. CONCLUSIONS: The cytotoxicity of the four catechins to LoVo cells is significantly different. The difference is associated with their effects on cell cycle and induction of apoptosis in LoVo cells.

Apoptosis↗
PubMed2000

[Design and optimization of a centrifugal pump for CPCR].

Requirements for an optimal centrifugal pump, the vital component in the equipment for cardiopulmonary cerebral resuscitation(CPCR), have been presented. The performance of the Sarns centrifugal pump (Sarns, Inc./3M, Ann arbor, MI, U.S.A) was tested. The preliminarily optimized model for CPCR was designed according to the requirements of CPCR and to the comparison and analysis of several clinically available centrifugal pumps. The preliminary tests using the centrifugal pump made in our laboratory(Type CPCR-I) have confirmed the design and the optimization.

Cardiopulmonary Bypass↗
PubMed2000

[Analysis of refractive state after excimer laser photorefractive keratectomy in myopia].

OBJECTIVE: To evaluate refractive state after excimer laser photorefractive keratectomy (PRK) in patients with myopia. METHODS: 234 cases(391 eyes) followed up for two years were divided into two groups, group I: mild and moderate myopia(< or = -6.00 D), 228 eyes; group II: High myopia(> -6.00 D), 163 eyes. The refractive state of patients at three, six, twelve and twenty-four months postoperatively were monitored. RESULTS: At two years after photorefractive keratectomy (PRK), refractive regression (> -0.5 D), overcorrection(> 1.00 D), undercorrection(> 1.00 D), postoperative residual astigmatism postoperative astigmatism and hyperopia shift in group I were 1.7%, 4.4%, 5.7%, 12.8%, 7.4% and 7.5% respectively, while in high myopia group were 15.9%, 4.9%, 23.3%, 29.7%, 31.1% and 6.7% respectively. CONCLUSION: The results prove that photorefractive keratectomy is an effective, precise, stable and safe method for correction of mild and moderate myopia, but insufficient for high myopia.

Adolescent↗
PubMed2000

[The diagnostic and prognostic values of assay of serum vascular endothelial growth factor in epithelial ovarian cancer].

OBJECTIVE: To detect the level of the preoperative serum vascular endothelial growth factor (VEGF) in patients with epithelial ovarian cancer, and to evaluate the correlation between preoperative serum VEGF level and prognosis of epithelial ovarian cancer. METHODS: Forty-one patients with epithelial ovarian cancer (EOC), 10 patients with borderline ovarian tumor (BOT), and 25 women with benign ovarian tumor (BET) were included as three study groups, while 20 healthy women were selected as a control group. Enzyme-linked immunosorbent assay (ELISA) was utilized to measure the serum VEGF level. RESULTS: The serum VEGF levels in patients with EOC were higher than those in patients with BOT, or with BET, or those in healthy women. The median and ranges of serum VEGF levels were as follows: EOC: median 415.0 pg/ml, range 110-2,120 pg/ml; BOT: median 312.5 pg/ml, range 100-1,250 pg/ml; BET: median 170 pg/ml, range 70-925 pg/ml; healthy women: median 165 pg/ml, range 100-735 pg/ml. When median preoperative serum VEGF levels were grouped by tumor stages, histological grade of tumor cells, histological type of the tumor, lymph node involvement, and omentum involvement, significant correlations between serum levels of VEGF and histological grade, lymph node involvement and omentum involvement were found. The patients with high serum VEGF appeared to be accompanied with poor 3-year survival. CONCLUSIONS: Preoperative serum VEGF levels seemed to be correlated with the malignant behavior of ovarian cancer, which might provide some prognostic value.

Adult↗
PubMed1999

Development and optimization of anti-HIV nucleoside analogs and prodrugs: A review of their cellular pharmacology, structure-activity relationships and pharmacokinetics.

Significant improvements in antiviral therapy have been realized over the past 10 years. Numerous nucleoside analogs, as well as prodrugs of active compounds, have been synthesized and tested for anti-HIV activity. In addition to the five nucleoside analogs currently used clinically for the treatment of HIV infection, a broad spectrum of anti-HIV nucleoside analogs (including 2',3'-dideoxynucleoside analogs, oxathiolanyl 2',3'-dideoxynucleoside analogs, dioxolanyl 2',3'-dideoxynucleoside analogs, carbocyclic 2',3'-dideoxynucleoside analogs and acyclic nucleoside analogs) and their prodrugs (including ester prodrugs, phospholipid prodrugs, dihydropyridine prodrugs, pronucleotides and dinucleotide analogs), targeted at HIV reverse transcriptase, are reviewed with focus on structure-activity relationships, cellular pharmacology and pharmacokinetics. Several of these anti-viral agents show promise in the treatment of AIDS.

Journal Article↗
PubMed1999

[Effects of long-term exposure to lower concentration of carbon disulfide on cardiovascular system of workers in a viscose rayon factory].

An epidemiological cross-sectional study was conducted on 99 workers exposed to lower concentration of carbon disulfide in a viscose rayon factory for a long time and 28 non-exposed ones in the same factory. Blood pressure, serum lipoproteins and electrocardiograph were detected. The results showed that neither diastolic blood pressure nor systolic one between exposed group and control group was obviously different All indicators of serum lipids and lipoproteins were not significantly different except the lipoprotein(a) of exposed group was significantly higher than that of control group, and the risk of abnormal electrocardiogram in the workers exposed to carbon disulfide was 1.1 times of those non-exposed ones but with no statistical significance. The results suggest that lipoprotein(a) can be used as a sensitive indicator for the cardiotoxic effects of carbon disulfide.

Adult↗
PubMed1999

Mutagenic properties of the 8-amino-2'-deoxyguanosine DNA adduct in mammalian cells.

The DNA adduct 8-amino-2'-deoxyguanosine (8-amino-dG) is found in liver DNA of rats treated with the hepatocarcinogen 2-nitropropane. Site-specifically modified oligodeoxynucleotides were used to explore the mutagenic potential of 8-amino-dG in simian kidney (COS-7) cells. Oligodeoxynucleotides (5'-TCCTCCTX1G2CCTCTC and 5'-TCCTCCTG1X2CCTCTC, X = dG or 8-amino-dG) with the lesion positioned at codon 60 or 61 of the non-coding strand of the human c-Ha- ras1 gene were inserted into single-stranded phagemid vectors and transfected into COS-7 cells. The progeny plasmid obtained was used to transform Escherichia coli DH10B. Transformants were analyzed by oligodeoxynucleotide hybridization and DNA sequencing to establish the mutation frequency and spectrum produced by the modified base. The correct base, dCMP, was incorporated preferentially opposite 8-amino-dG at X1and X2. When 8-amino-dG was at X1, targeted GNH2-->T transversions were detected, along with smaller numbers of GNH2-->A transitions and GNH2-->C transversions. When the adduct was at X2, only GNH2-->T transversions were observed. The frequencies of targeted mutation at X1and X2were 2.7 and 1.7%, respectively. Mutation frequency and mutagenic spectrum were sequence context dependent. In addition, non-targeted G-->T transversions, accompanied by some G-->A transitions, were detected 5' to 8-amino-dG when the lesion was at X2. We conclude that 8-amino-dG is a mutagenic lesion, generating G-->T and G-->C transversions and G-->A transitions in mammalian cells.

Animals↗
PubMed1999

[Serum sex hormone and urinary metabolites of male workers exposed to carbon disulfide].

Serum luteotropic hormone(LH), follicle-stimulating hormone (FSH), prolectin(PRL) and testosterone (T) were determined by radioimmunoassay methods in 50 workers exposed to carbon disulfide(CS2) in a viscose rayon factory. Urinary excretion of 2-thio-thiazolidine-4-carboxilic acid (TTCA) in workers by the end of work shift was analyzed with modified high-performance liquid chromatography. The working conditions of the factory had not been changed since 1950s. The concentration of CS2, determined by Multigas Monitor (type 1320) in workplace, was (14.4 +/- 4.62) mg/m3. The results showed that: (1) serum FSH of CS2 group (10.04 +/- 7.35)IU/L was significantly higher than that of control group (7.50 +/- 7.07 IU/L), PRL of CS2 group (5.72 +/- 4.18) ng/L was significantly lower than that of control group (6.89 +/- 4.64 ng/L). Serum LH was declined with the increase of time exposed to CS2, (2) urinary TTCA in CS2 group was 1.072 +/- 1.013 mg/g Cr. Serum FSH was declined with the increase of TTCA excretion. The results suggested that the function of endocrine system was disturbed in workers exposed to CS2.

Adult↗
PubMed1999

Candidate EPA, NIOSH method for determining carbon disulfide in air with capillary gas chromatography by orthogonal design.

This paper describes a candidate NIOSH EPA method for the determination of carbon disulfide in the air of workplaces with capillary gas chromatography using an orthogonal design. This method is designed to replace the packed column of the NIOSH method with a capillary column. The first part of this work concerned the setup of the method, particularly the choice of chromatographic parameters and finding their main favorable working ranges. The second part, using the statistical method orthogonal design, focused on optimizing the GC conditions, which were: column temperature, T(c) = 90 degrees C; injector temperature, T(i) = 140 degrees C; U section detector temperature, FPDU = 160 degrees C; L section detector temperature, FPDL = 210 degrees C; flow rate of carrier gas, F(c) = 20 cm/s; split ratio = 1/70; and injection volume = 1 microL. The quality control test showed that the coefficient of intra-day variation (CV) was 2.21%. A good logarithm linear correlation between the standard solutions and their peak areas was obtained. In general, the method reported here seems a valid candidate for a NIOSH EPA method due to its high precision and accuracy.

Air Pollutants↗
PubMed1999

Study on relationship between carbon disulfide exposure and symptoms and signs of nervous system in workers.

The relationship between carbon disulfide (CS2) and the symptoms and signs of nervous system in rayon workers was investigated. In a cross sectional study of CS2-exposed workers from the viscose industry and controls, data on neurological symptoms and clinical neurological examination were evaluated. The exposed subjects includes 326 workers and 105 workers from the same factory, without exposure to CS2 or to any other neurotoxic agents, served as controls. The median exposure to CS2(8 h time weighted) in the low-level exposure group was 4.6 mg/m3, and 18.3 mg/m3 in high-level exposure group. Non-conditional multiple logistic regression analysis was employed for evaluating statistical differences by using SAS software. In the analysis, age, sex, work time, body mass index (BMI), smoking and drinking habits, educational background and marriage status were controlled. The odds ratio (OR) significantly increased of some symptoms in workers exposed to CS2 at levels below 10 mg/m3, as compared to controls. The dose-effect relationship between the exposure to CS2 and the symptoms of nervous system was demonstrated. In terms of neurological parameters, no other abnormal change but that in temperature sensitivity was observed in workers exposed to CS2. In conclusion, the influence of low level CS2 on nervous system of workers should not be ignored.

Carbon Disulfide↗
PubMed1999

Haploinsufficiency of CBFA2 causes familial thrombocytopenia with propensity to develop acute myelogenous leukaemia.

Familial platelet disorder with predisposition to acute myelogenous leukaemia (FPD/AML, MIM 601399) is an autosomal dominant disorder characterized by qualitative and quantitative platelet defects, and propensity to develop acute myelogenous leukaemia (AML). Informative recombination events in 6 FPD/AML pedigrees with evidence of linkage to markers on chromosome 21q identified an 880-kb interval containing the disease gene. Mutational analysis of regional candidate genes showed nonsense mutations or intragenic deletion of one allele of the haematopoietic transcription factor CBFA2 (formerly AML1) that co-segregated with the disease in four FPD/AML pedigrees. We identified heterozygous CBFA2 missense mutations that co-segregated with the disease in the remaining two FPD/AML pedigrees at phylogenetically conserved amino acids R166 and R201, respectively. Analysis of bone marrow or peripheral blood cells from affected FPD/AML individuals showed a decrement in megakaryocyte colony formation, demonstrating that CBFA2 dosage affects megakaryopoiesis. Our findings support a model for FPD/AML in which haploinsufficiency of CBFA2 causes an autosomal dominant congenital platelet defect and predisposes to the acquisition of additional mutations that cause leukaemia.

Amino Acid Sequence↗
PubMed1999

Platelet-activating factor receptor mRNA is localized in eosinophils and epithelial cells in rat small intestine: regulation by dexamethasone and gut flora.

Platelet-activating factor (PAF) is a potent mediator involved in bowel injury. We investigated PAF receptor transcription and its mRNA localization in the small intestine of normal (conventionally fed) and germ-free rats, by competitive polymerase chain reaction (PCR) and in situ hybridization. A dose of PAF (1.5 microg/kg, i.v.) insufficient to cause gross bowel injury was injected into rats. Some rats were pretreated with dexamethasone (1 mg/kg). We found: (1) PAF receptor (PAF-R) mRNA localized predominantly in lamina propria eosinophils and in epithelial cells; (2) PAF increased PAF-receptor signals in the epithelial cells; (3) Dexamethasone depleted eosinophils in the intestine and markedly decreased PAF-receptor transcripts; the response to PAF was also weaker than control rats; (4) Germ-free rats had less PAF-R mRNA than normal rats, and showed a weaker response to PAF than conventionally fed rats. Thus, we conclude: (1) PAF receptor mRNA is constitutively expressed in the epithelium and in lamina propria eosinophils in the intestine. (2) PAF-R transcription is up-regulated by PAF and gut flora, mostly in the epithelium. (3) PAF-R transcription is down-regulated by glucocorticoids, mainly as a result of eosinophil depletion. These results suggest a functional role for PAF receptors both in host defence and the inflammatory response in the small intestine.

Animals↗