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Biomedical subjects

W Tan

Publications and source records attributed to W Tan.

At least 73 records · Page 4Linked to original sources
PubMed1999

[Effects of metalloproteinases on pulmonary fibrosis by bleomycin in rats].

OBJECTIVE: Matrix metalloproteinases (MMPs) are the mediators for dynamic equilibrium of extracellular matrix. The purpose was to investigate the effects of metalloproteinases on the development of pulmonary fibrosis. METHODS: The expression and activity of metalloproteinases of alveolar macrophage, and fibroblasts were evaluated on rats with pulmonary fibrosis induced by bleomycin. RESULTS: The activity of collagenase was low in the macrophage and fibroblast in control group, 20.4 x 10(-7) U/cell and 30.6 x 10(-7) U/cell respectively. There was an increase in the first and fourth week groups of bleomycin rats. The highest level of activity of alveolar macrophages was 258.0 x 10(-7) U/cell in first week group. A peak of enzymatic activity was found in 4th week group (289.0 x 10(-7) U/cell). The mRNA of MMP-1, MMP-2 were expressed at lower levels in the normal lung tissue and there was an increase in first week, and fourth week group of bleomycin rats with a peak in one week group. CONCLUSIONS: The regulation of metalloproteinases might play an important role in the development of pathological processes in pulmonary fibrosis.

Animals↗
PubMed1999

[Recovery of gastrointestinal motility following laparoscopic versus open cholecystectomy].

OBJECTIVE: To investigate the recovery of gastrointestinal motility after laparoscopic cholecystectomy (LC) and open cholecystectomy (OC). METHODS: Motilin (MOT), gastrin (GAS), electrogastrogram (EGG), the peristaltic sound recovery timing (PSRT) and the anorectum exhaust timing (AET) were determined in 30 patients having LC and 18 patients having OC. RESULTS: MOT, GAS, EGG frequency and EGG amplitude on the first, second and third day after operation in LC group were not significantly different in comparison with preoperative data (P > 0.05), but significant difference on the first and second postoperative day compared with preoperative data and data of the the LC group (P < 0.05). The PSRT and AET in the LC group were much shorter in comparison with the OC group (P < 0.05). CONCLUSIONS: The recovery of gastrointestinal motility after LC is earlier than OC, which justifies early feeding for patients after LC.

Cholecystectomy↗
PubMed1999

[A mutation specific polymerase chain reaction for detecting hepatitis B virus genome with A-to-C mutation at nt585].

OBJECTIVE: To investigate the prevalence of hepatitis B virus (HBV) nt585 A-to-C mutants in China. METHODS: A mutation specific polymerase chain reaction (msPCR) was established for amplifying HBV DNAs with A-to-C mutation at nt585. Two sets of primer pairs with same sequences except for one base at 3' terminus were designed and synthesized according to 48 of the known HBV genome sequences and the popular HBV subtypes, adr and adw, in China. RESULTS: 57 of HBV S gene fragments amplified by a nested PCR from different and child adult hepatitis B patients were characterized by using the msPCR. It was shown that HBV mutants with A-to-C mutation at nt585 could be confirmed. CONCLUSION: The msPCR is a specific and sensitive method for detecting the HBV nt585 A-to-C mutants.

Adult↗
PubMed1998

Characterisation and partial purification of cellular factors interacting with a negative element on human papillomavirus type 1 late mRNAs.

We have previously identified and characterized an AU-rich inhibitory RNA element located in the 3' untranslated region on late human papillomavirus type 1 (HPV-1) mRNAs. This sequence is active in the absence of virus proteins and interacts specifically with cellular proteins, which presumably mediate the inhibitory activity. Here we have characterized and partially purified five proteins (80-, 52-, 46-, 44-, and 38-kDa) that interact independently and specifically with an AU-rich inhibitory sequence on HPV-1 late mRNAs. Dephosphorylation of the proteins resulted in loss of RNA binding activity. Proteins similar to the 38-, 44-, and 46-kDa proteins were detected also in murine epithelial cells, whereas proteins corresponding to the 80- and 52-kDa proteins were not. Since the inhibitory HPV-1 sequence is active in murine epithelial cells, the results suggested a role for the 38-, 41, and the 46-kDa proteins in the regulation of HPV-1 late gene expression.

Animals↗
PubMed1998

Identification and determination of phase I metabolites of propafenone in rat liver perfusate.

Propafenone (PF) is a class 1C antiarrhythmic agent. To study the mechanisms of PF interactions with dietary nutrients in isolated, perfused rat livers, metabolites of PF in liver perfusate were identified and an analytical method was developed for these metabolites plus parent drug. Identification of phase I metabolites was performed using HPLC/MS equipped with a Lichrospher RP-18 column and tandem mass spectrometry (MS/MS) with electrospray and atmospheric pressure chemical ionizations. Three major metabolite peaks, whose protonated molecular ions were m/z 358, 358 and 300, were identified as a propafenone derivative hydroxylated in the omega-phenyl ring (omega-OH-PF), 5-hydroxypropafenone (5-OH-PF), and N-despropylpropafenone (N-des-PF). The levels of omega-OH-PF, 5-OH-PF, N-des-PF and PF were determined simultaneously by HPLC with UV detection at 210 nm and a mobile phase of 0.03% triethylamine and 0.05% phosphoric acid in water-acetonitrile-methanol (45:20:35, v/v/v) after extraction with 5 ml diethyl ether at pH 10.0 and evaporation of solvent under nitrogen. The results revealed that omega-OH-PF, which was not found in humans, was the major metabolite of PF in rat liver perfusate, not 5-OH-PF which is the major metabolite in human plasma.

Animals↗
PubMed1998

mRNA instability elements in the human papillomavirus type 16 L2 coding region.

Human papillomavirus capsid proteins L1 and L2 are detected only in terminally differentiated cells, indicating that expression of the L1 and L2 genes is blocked in dividing cells. The results presented here establish that the human papillomavirus type 16 L2 coding region contains cis-acting inhibitory sequences. When placed downstream of a reporter gene, the human papillomavirus type 16 L2 sequence reduced both mRNA and protein levels in an orientation-dependent manner. Deletion analysis revealed that the L2 sequence contains two cis-acting inhibitory RNA regions. We identified an inhibitory region in the 5'-most 845 nucleotides of L2 that acted by reducing cytoplasmic mRNA stability and a second, weaker inhibitory region in the 3' end of L2. In contrast, human papillomavirus type 1 L1 and L2 genes did not encode strong inhibitory sequences. This result is consistent with observations of high virus production in human papillomavirus type 1-infected tissue, whereas only low levels of human papillomavirus type 16 virions are detectable in infected epithelium. The presence of inhibitory sequences in the L1 and L2 mRNAs may aid the virus in avoiding the host immunosurveillance and in establishing persistent infections.

Capsid↗
PubMed1998

Modulation of nicotinic AChR channels by prostaglandin E2 in chick sympathetic ganglion neurons.

The effects of prostaglandin E2 (PGE2), an important metabolite of arachidonic acid, were studied on the activity of nicotinic AChR channels in cultured chick sympathetic ganglion neurons. In whole cell recordings, PGE2 (25 nM) inhibited significantly the ACh-evoked macroscopic current. In cell-attached patch recordings, PGE2 significantly inhibited single AChR channel currents as a result of a decrease in the frequency of channel opening, with no change in open time and conductance. PGE2 did not alter the extent or rate of agonist-induced desensitization of the AChR channels. These effects are specific since the related compound PGD2 had no effect on AChR channel function. Because there is an abundant endogenous production of PGE2 within sympathetic ganglia in response to certain stimuli, the inhibition of AChR channel function by PGE2 could serve an important role to modulate synaptic transmission in the sympathetic nervous system.

Animals↗
PubMed1998

Automated detection of hydrogen sulfide release from thiosulfate by Salmonella spp.

Hydrogen sulfide production is used in conventional tests for identification and differentiation of Salmonella spp. from other species of Enterobacteriaceae, and a black precipitate on agar media is the indicator of the reaction. Selective liquid media were formulated for automated optical detection of H2S in salmonellae using the BioSys instrument. The media contained thiosulfate and ferric ammonium citrate, and production of H2S caused copious black pigmentation of the broth. Combination of the H2S indicators with dulcitol or xylose as fermentable carbohydrate, lysine, ornithine or arginine to induce decarboxylase activity, and Tergitol 4 as inhibitor selectively identified six Salmonella spp. by a sharp drop in transmittance at 585 nm. The time for detection of transmittance changes was inversely proportional to initial numbers of CFU in the media: 10 h for 10(5) CFU/ml and 17 h for 10(1) CFU/ml. No detection was observed in six non-Salmonella species of Enterobacteriaceae tested.

Carboxy-Lyases↗
PubMed1998

[Chemoprotection by green tea against the formation of food-borne carcinogen 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP)-DNA adducts in rats].

OBJECTIVE: The food-borne mutagen 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP) induces colon and mammary gland tumors in rats and has been implicated in the etiology of human cancer, particularly colorectal cancer. This study was conducted to examine the potential chemopreventive effect of Chinese green tea against PhIP-DNA adduct formation in rats and its possible mechanisms. METHODS: Sprague-Dawley rats were maintained on freshly prepared aqueous extract of Chinese green tea (3%) or tap water as the sole source of drinking fluid for 10 days prior to administration with a single dose of PhIP (10 mg/kg body wt) by oral gavage. Rats were sacrificed at 20 h after PhIP treatment and PhIP-DNA adducts in the colon, heart, lung, and liver were analyzed using 32P-postlabeling technique. The activity of cytosolic glutathione S-transferases (GSTs) in the liver, lung and colon mucosa was also determined using CDNB as substrate. RESULTS: The levels of PhIP-DNA adducts in the four tissues of rats treated with PhIP alone were highest in the colon (53 +/- 9 adducts/10(8) nucleotides), followed by heart (41 +/- 14 adducts/10(8) nucleotides) and lung (22 +/- 5 adducts/10(8) nucleotides), but much lower in the liver (5 +/- 3 adducts/10(8) nucleotides). Rats pre-treated with green tea had significantly reduced levels of PhIP-DNA adducts, with the inhibition rates being 59%-80%, respectively. While the organ distribution profile of the adducts was not altered by tea treatment as compared with controls given PhIP alone. The GST activity towards CDNB in hepatic, colonic and lung cytosols appear not to be modified by drinking green tea. CONCLUSION: These results support a protective role for green tea against PhIP-initiated carcinogenesis in rats and suggest that consumption of green tea may have significant impact in chemoprevontion against human cancer presumably related to PhIP and other heterocyclie amines.

Animals↗
PubMed1998

[Study on the effects of hyaluronic acid-streptomycin perfusion through the round window on the function and morphology in guinea pig inner ears].

To investigate the effects of the hyaluronic acid-streptomycin (HA-SM) perfusion through round window on the function and morphology of the inner ear in guinea pig, membrous labyrinth mapping, temporal bone section after celloidin embedding, transmission electron microscopy, electrocochlegraphy (ECochG) and electronystagmography (ENG) were examined. The nystagmus duration induced by caloric test was obviously reduced in comparison with that of the preoperation (P< 0.01), while the action potential(AP) by ECochG was not obviously changed. The sensory cells of estibular organs were severely damaged, while the morphology of corti's organs were significantly damaged after HA-SM perfusion. The results suggest that the HA-SM perfusion through the round window may selectively destroy the vestibular function, whereas the auditory function is not obviously damaged.

Animals↗
PubMed1998

[Chemoprevention of 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine-induced carcinogen-DNA adducts by Chinese cabbage in rats].

OBJECTIVES: To examine the preventive effect of Chinese cabbage (Brassica chinensis) against colon carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced PhIP-DNA adduct formation in rats and its possible mechanism. METHODS: Sprague-Dawley rats were maintained for 10 days on lab chow or chow containing 20% (w/w) freeze-dried cabbage powder prior to administration of a single dose of PhIP (10 mg/kg) by oral gavage. Rats were sacrificed at 20 h after PhIP treatment and PhIP-DNA adducts in the colon, heart, lung, and liver were analyzed using 32P-postlabeling technique. Levels of hepatic cytochrome P450 (CYP) 1A1 and 1A2, as indicated by 7-ethoxyresorufin O-deethylase and 7-methoxyresorufin O-demethylase activity, and cytosolic glutathione S-transferases (GST) towards CDNB in the liver, lung and colon mucosa were measured. RESULTS: Rats pre-treated with Chinese cabbage and given a single dose of PhIP had reduced levels of PhIP-DNA adducts in the colon, heart, lung and liver, with an inhibition rate of 82.3, 60.6, 48.4 and 48.9%, respectively (P < 0.01). Enzyme assays revealed that both CYP1A1 and 1A2 were induced by cabbage, but the induction was preferential for CYP1A1 over 1A2 (80.6% vs 50.2%). GST activity towards CDNB in the liver and lung, but not colon, was also significantly induced by the cabbage. CONCLUSION: The results indicate a preventive effect of Chinese cabbage against PhIP-initiated carcinogenesis in rats and the mechanism is likely to involve induction of detoxification enzymes.

Animals↗
PubMed1998

[Surgical injuries influence on release of endothelin-1 and local blood perfusion of amputated extremities].

OBJECTIVE: To observe influence of amputations and surgical injuries on synthesis and release of endothelium-derived endothelin-1, and local blood perfusion of amputated extremities. METHOD: The plasma endothelin-1 concentrations of 18 patients preoperatively and postoperatively and the endothelin-1 concentrations of femoral artery wall in 80 SD rats were determined using radioimmunoassay technique before and after amputation. Local blood perfusion of amputated extremities in rats were determined using laser Doppler flowmetry. RESULT: The plasma endothelin-1 concentrations in the patients with surgical injuries increased obviously, reached peak value at fourth hour postoperatively, being approximately 3 times of that of the control group. The endothelin-1 concentrations of femoral artery wall in amputated rats also increased, reached peak value at second hour after amputation, being approximately 2 times of that of the control group, and then decreased gradually, at the same time the local blood perfusion decreased, reached its lowest value at second hour after amputation, being only 25 percent of the control value. The endothelin-1 concentration of rat femoral artery wall was negatively relative to local blood perfusion (r = -0.83). CONCLUSION: Injuries enhance synthesis and release of endothelin-1. It is probably one of the main causes of vasospasm after injuries.

Adolescent↗
PubMed1998

[Cloning and sequencing of cDNA in NS3 region of Chinese hepatitis G virus isolated from Henan Province].

To study the genetic characteristics of non-structural region 3 of HGV in China, a HGV-RNA positive sample was collected from Henan. HGV RNA was extracted and amplified by RT-nested-PCR. We got four overlap fragments and they were cloned into plasmid vector pcDNA II. The cDNA was sequenced by the Sanger's method. Nucleotide homology between Henan strain and other reported HGV isolates (PNF2161, R10291, GBV-C) was 85.7% to 93.8% over the 2137 nucleotides examined. Comparison of amino acid sequence deduced from Henan strain with that of other isolates showed 96.1% to 97.7% homology. Three amino acid variations were found in NS3 region of all the three Chinese isolates of HGV. In addition, a N-glycosylation site was found in the NS3 region of all the six isolates.

Amino Acid Sequence↗
PubMed1998

[Detection of hepatitis G virus infection among clinical patients with hepatitis/liver diseases in China by reverse transcription-nested polymerase chain reaction].

According to two highly conserved genome sequences within the helicase(NS3) region and 5'-uncoding(5' UTR) region, we designed two sets of primer pairs to detect HGV RNA by RT-nested PCR in order to study HGV infection in Chinese population. Three hundred and fifty-four serum specimens of various liver diseases were collected from Beijing, Qin Huangdao and Henan areas. Seventy-nine out of 354(22.3%) specimens were HGV RNA positive. Among 254 known clinical hepatitis/liver disease samples, 50(19.6%) were HGV RNA positive. Thirteen HGV RNA positive samples(30.2%) were derived from 43 cryptogenic or nonA-E hepatitis. In 57 commercial blood donors who were antibody positive to HCV 16(30.2%) were HGV RNA positive, suggesting HGV infection is common in various population. It may be an etiological factor which leads to nonA-E hepatitis and post-transfusion hepatitis.

5' Untranslated Regions↗
PubMed1998

[Identification of hepatitis C or/and G virus RNA in one tube by reverse transcription nested polymerase chain reaction].

Hepatitis C and G viruses belong to the flaviviridae family. They have similar modes of transmission. The dual infection of HGV and HCV were reported. A simultaneous detection for HCV or/and HGV was established by reverse transcription nested polymerase chain reaction(RT-nested PCR). The primers were derived from the 5' non-coding region of HCV and NS3 region of HGV, and the length of the PCR product was between 170 bp and 300 bp. RT-nested PCR can be finished in one test tube and HGV and/or HCV can be detected simultaneously in one RT-nest PCR. 153 samples were detected by his method. Our results showed that the established assay is useful for screening and identification of HCV or/and HGV RNA. This method is simple and specific practicable.

5' Untranslated Regions↗
PubMed1998

[Rapid construction of recombinant baculovirus carrying hepatitis B virus surface antigen gene by using a novel baculovirus shuttle vector(Bacmid)].

In order to express the HBV surface antigen (HBV) efficiently by using the Bac-to-Bac system and to produce HBsAg for diagnosis and vaccine development of HBV, a recombinant donor plasmid pFB-BS carrying HBsAg gene was constructed. The gene was inserted into shuttle plasmid (Bacmid) in E. coli DH10Bac with the help of Tn7 transposition system. The recombinant Bacmid was examined by PCR and transfected to Sf9 cells. HBsAg was expressed under the control of polyhedrin promoter of baculovirus in insect cells and was identified by ELISA. The quantity of the expression reached to 2 micrograms/10(6) cells and most production was within cells. Our data suggested that the Bac-to-Bac system can be used successfully and rapidly in the expression of viral gene.

Baculoviridae↗
PubMed1998

An improved, inexpensive method for the large-scale purification of human nerve growth factor.

Human nerve growth factor (hNGF) was purified to near homogeneity on a large scale from human term placenta with an improved and inexpensive method. The purification procedure included tissue homogenization, ultrafiltration and single CM-cellulose column chromatography. The purified hNGF was a 14.4-kDa protein with an isoelectric point of approximately 9.3. The specific activity of the purified hNGF was approximately 38000 units/mg, and the activity was completely inhibited by the monoclonal antibody against recombinant hNGF (rhNGF). Western-blot analysis showed that the purified hNGF could interact with the monoclonal antibody against rhNGF.

China↗