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Biomedical subjects

W Chen

Publications and source records attributed to W Chen.

At least 739 records · Page 41Linked to original sources
PubMed1997

The application of a novel thrombin sensitive site in genetic engineering.

To obtain high efficiency of cleavage of thrombin in fusion protein containing alpha-ANP fused to Ref peptides, the linker sequence designed as VIAGR which was different from GVRGPR formerly used was studied. Plasmid pHL carrying the fusion gene Ref-NT-ANP downstream from PL promoter was derived from expression vector pLY1 by inserting the fragment of NT-ANP into it. The expression of fusion gene was induced at 42 degrees C, and the interested protein Ref-NT-ANP accumulated as inclusion bodies was isolated by gradient centrifuge and then dissolved in 7 mol/L guanidinehydrochloride (Gdn-HCl). After dilution, renaturation and dialyzation, the cleavage of thrombin was examined using samples with 1.1 mol/L Gdn-HC1 and samples free of Gdn-HCl respectively. Digestion result showed that the novel-adopted cleavage sequence was highly sensitive to thrombin when the substrate dissolved in 1.1 mol/L Gdn-HCl. The time needed for 87% cleavage (the ratio of substrate to thrombin was 50 micrograms/u) was less than 24 hours. This sequence described here which was specifically recognized by thrombin might be broadly applied in other fusion systems.

Atrial Natriuretic Factor↗
PubMed1997

[Twenty-eight alphavirus strains isolated from mosquitoes and ticks captured from Hainan Island, China].

Virus isolation was carried out from mosquitoes and ticks captured in nature from Hainan Island of China from 1983-1988. Twenty-eight non-dengue and non-Japanese encephalitis viral strains were isolated from different places, of which 27 strains were recovered from different species of mosquitoes and 1 strain from ticks. At the Division of Vector-Bore Viral Diseases, National Center for Infectious Diseases, Centers for Disease Control, USA, identification of virus family and virus genus on these 28 viral strains was conducted by the use of a complete set of internationally standardized antibodies against arboviruses and by means of indirect immunofluorescence. Results proved that all these 28 viral strains belonged to the Genus Alphavirus of the Family Togaviridae.

Alphavirus↗
PubMed1997

[Clonning and sequencing of partial gene of hepatitis G virus (HGV) from Nanjing of China].

Partial gene of hepatitis G virus (HGV) was cloned and sequenced from the serum of a patient with post-transfusion hepatitis C in Nanjing of China by reverse transcription-polymerase chain reaction (RT-PCR). The sequence showed 89.09%, 92.12%, 87.27%, 93.94% nucleotide identity over the corresponding region of HGU44402, HGU45966, HGU36380 in America and HGV isolate in Hebei Province of China respectively. Forty patients with post-transfusion hepatitis C and thirty patients with hepatitis non A-E were detected for HGV RNA by RT-PCR, the HGV RNA positive rate were 10.00% and 6.67% respectively.

Base Sequence↗
PubMed1997

[Expression of human betaIVS- II -nt 654 C --> T allele in HeLa cell].

OBJECTIVE: To establish a cell model expressing human betaIVS- II -nt 654C --> T allele (beta654 mutant). METHODS: DNA fragment of entire beta-globin gene encompassing the codon region and poly(A) signal of the allele was amplified by long PCR from the genomic DNA of a homozygote with beta65.4 mutation. The amplified fragments were cloned into the Hind III and Xba I sites of the pcDNA3.1 vector. After reidentification of the clone with beta654 mutant by DNA sequencing, the recombinant plasmid was transfected into HeLa cell using liposome method. The expression of the beta654 mutant gene in the transfected cells was detected by RT-PCR. RESULTS: Both the normally processed beta globin mRNA (183bp) and aberrant processed beta globin mRNA (256bp) were identified in the transfected HeLa cells, while no RT-PCR product was detected in the controls. CONCLUSION: The transfected HeLa cells can express human beta654 allele.

Alleles↗
PubMed1997

[Structural identification of carboxylic esters by pyrolysis gas chromatography].

A pyrolysis gas chromatographic method has been investigated for structural identification of carboxylic esters. The method can be applied to identify not only pure components, but also those separated by thin layer chromatography and scraped from the TLC plate without removing the adsorbent. The samples were pyrolyzed in tube furnace pyrolyzer at 500 degrees C (conventional pyrolysis) or were pyrolyzed at 550 degrees C after mixing with soda-lime powder (pyrolysis with soda-lime). Some esters such as iso-octyl palmitate, glycerol monostearate and diethyl phthalate were pyrolyzed. The pyrolysis products were identified by comparing with the known. The parent alcohols of monohydric and polyhydric alcohol esters can be determined respectively according to alcohols, alkenes produced on pyrolysis and dehydrated products of polyhydric alcohol at high temperature. The parent acids of monocarboxylic esters can be determined according to carboxylic acid produced on conventional pyrolysis or corresponding alkane formed from decarboxylation of parent acids on pyrolysis with soda-lime. For esters formed from dicarboxylic acids that can be dehydrated to produce five-, six-membered cyclic ketones or can be dehydrated and decarboxylated simultaneously to produce five-, six-membered cyclic acid anhydrides, parent acids can be determined according to corresponding cyclic ketones or cyclic acid anhydrides. This method is useful for identification of common carboxylic esters. When the compound or the component of the mixture was confirmed to contain ester-group by infra-red spectroscopy, PGC or TLC-PGC can be employed to make further identification.

Carboxylic Acids↗
PubMed1997

[Ann applied to the prediction of vibration frequencies of octahedral modes (v1 and v2) of MX6(n-) ions (X = F, Cl, Br, I)].

Artificial neural networks back-propagation algorithm was applied to the prediction of vibration frequencies of v1 and v2 modes of octahedral hexahalide (MX6(n-)). Three-layer networks with one and two output nodes were used. Two inertia terms and training step controlling scheme were adopted to weights adjustment. The result of one output node networks has little difference from that of two output nodes networks. The frequencies of [Mof6]2-, [BiF6]- and [AuF6]- from literature are a great deal different from those calculated or predicted values.

English Abstract↗
PubMed1997

[Structural characterization of copper-phthalocyanine thin solid films by FTIR spectroscopy].

The structure of tris- (2, 4-di-t-amylpheoxy) - (8-quinolinoxy) copper phthalocyanine (CuPc) thin solid films has been characterized by Fourier transform infrared (FTIR) transmission, polarized transmission and reflection absorption (RA) spectroscopy. The following conclusions can be obtained from the above measurements: (1)in LB films, the hydrocarbon chains of CuPc are in hexagonal or pseudohexagonal subcell packing, the CH2 asymmetric vibrational vector is oriented with respect to the substrate surface and the RA spectroscopy can distinguish the two CH2 streching modes of benzene cycle; (2)in sublimed films, the molecules of CuPc are out of order.

English Abstract↗
PubMed1997

Counseling clinic for pediatric weight reduction: program formulation and follow-up.

The feasibility and efficacy of an outpatient-based multicomponent weight reduction program was tested with 68 consecutively enrolled obese children and adolescents. The patients were invited to participate in an individualized six-session program that included parent involvement, diet education, exercise management and behavior modification by a culturally sensitive method. Fifty-six patients were followed up 1 year after treatment. Comparison at pretreatment, end-of-treatment and 1-year-after-treatment with respect to changes in degree of obesity, measured by weight-for-length index (WLI), showed statistically significant differences. Ninety-seven percent of participants were below their pretreatment WLI at the end-of-treatment examination, and 80% at 1-year-after-treatment follow-up. At 1-year-after-treatment, 59% showed a reduction in WLI of 0.1 or more, as compared with 38% of participants at end-of-treatment. Two parameters previously considered predictors of successful weight control, notably age of participants and percentage of weight lost during treatment, were significantly associated with a reduction in the degree of obesity after one year. Although the long-term efficacy cannot be determined, our results indicated that this comprehensive weight reduction program may have an encouraging effect on the weight status of obese Chinese children and adolescents.

Adolescent↗
PubMed1997

Amplification of GB virus-C/hepatitis G virus RNA with primers from different regions of the viral genome.

GB virus-C/hepatitis G virus (GBV-C/HGV) is a newly identified RNA virus. The aim of the study was to compare three primer pairs from the 5' untranslated region (5'UTR), envelope region 2 (E 2) and nonstructural region 3 (NS 3) of GBV-C/HGV genome for their ability to detect GBV-C/HGV RNA by polymerase chain reaction (PCR) assays. By using PCR with primers from different regions of the viral genome, serum GBV-C/HGV RNA was assayed in 200 at-risk individuals. The sensitivity of this assay was assessed by a titration experiment, and nucleotide sequences of the amplified products were determined directly. Of 200 serum samples, 43 (21.5%) were positive for GBV-C/HGV RNA with at least one of the primer pairs. The positive rates by 5'UTR, NS 3, and E 2 primers were 100%, 98%, and 84%, respectively, and the sensitivity of PCR assays using 5'UTR primers was 10 to 100 times more likely to detect GBV-C/HGV RNA than that of NS 3 and E 2 primers. The average homology of amplified targets to the prototype HGV genome was 89%, 80%, and 85% and the similarity between each amplified target was up to 100%, 90%, and 92% in the 5'UTR, E 2, and NS 3 regions, respectively. Therefore, the 5'UTR of GBV-C/HGV genome is highly conserved and primers deduced from this region can provideva sensitive and specific PCR assay for GBV-C/HGV RNA.

Base Sequence↗
PubMed1997

Production of platelet-derived growth factor by interleukin-1 beta and transforming growth factor-beta-stimulated retinal pigment epithelial cells leads to contraction of collagen gels.

PURPOSE: In an in vitro model of the later contractile stages of proliferative vitreoretinopathy, interleukin-1 beta (IL-1 beta) and transforming growth factor-beta (TGF-beta) stimulate the contraction of collagen gels by retinal pigment epithelial (RPE) cells. This contraction occurs after a lag period and appears not to be a direct effect of the cytokines but is mediated by another factor produced in the presence of the two cytokines. The nature of this factor has been investigated. METHODS: Human RPE cells were seeded onto collagen gels in the presence of IL-1 beta and TGF-beta. After 24 hours, the conditioned medium was removed and added to new collagen gels seeded with RPE cells, and the diameter of the collagen gels was measured after various intervals. The ability of the conditioned medium to effect contraction was determined after various treatments, including size fractionation, heating, trypsin digestion, and binding to heparin-Sepharose. The involvement of platelet-derived growth factor (PDGF) as a stimulator of contraction was tested with neutralizing antibodies and by polymerase chain reaction analyses of specific mRNAs. RESULTS: IL-1 beta and TGF-beta cause RPE cells to contract after a delay of up to 24 hours, whereas conditioned medium from cytokine-treated cells results in immediate contraction in a manner similar to that of serum. The factor in the conditioned medium causing immediate contraction was found to be heat-stable, trypsin-sensitive, and resistant to extremes of pH. It has a size of between 30 and 50 kDa and binds heparin. The factor in conditioned medium from cytokine-treated cells does not act in the presence of C-kinase inhibitors or cycloheximide, suggesting that signaling is mediated by way of protein kinase C and new protein synthesis. Stimulation of contraction by conditioned medium is inhibited by anti-PDGF antibodies, and contraction is stimulated by human PDGF. CONCLUSIONS: Contraction in the presence of cytokines is mediated by the production of PDGF or a PDGF-like molecule. This factor could have implications in the pathogenesis of proliferative vitreoretinopathy.

Cells, Cultured↗
PubMed1997

The mechanism of Epstein-Barr virus infection in nasopharyngeal carcinoma cells.

To investigate the relationship between Epstein-Barr virus (EBV) and nasopharyngeal carcinoma (NPC) cells, we examined the pathway of EBV infection in NPC cell lines. We used immunolocalization to investigate the EBV receptor (C3d-R) and polymeric immunoglobulin receptor [secretory component (SC) protein]. We incubated IgA anti-EBV and EBV particles with NPC cells and observed the EBV DNA signal by in situ polymerase chain reaction hybridization and polymerase chain reaction plus Southern blotting. We also colocalized SC protein and EBV RNA in NPC biopsy specimens. Results showed that: 1) NPC cells did not express the EBV receptor but did express SC protein in each line; 2) SC protein was also expressed in some tumor cells but not in untransformed squamous metaplastic epithelia in NPC biopsy specimens; 3) EBV could infect NPC cells through an EBV-IgA and SC complex and retained an EBV viral genome in their nuclei; SC expression could be down-regulated by EBV proteins; and 4) in biopsy specimens, a fraction of tumor cells showed SC protein expression; only a portion of tumor cells contained EBV, and of these cells only a few expressed SC protein. These findings indicate that EBV cannot infect untransformed nasopharyngeal squamous metaplastic epithelia but can enter NPC cells through IgA-mediated endocytosis.

Carcinoma↗
PubMed1997

Novel homozygous and compound heterozygous mutations of sterol 27-hydroxylase gene (CYP27) cause cerebrotendinous xanthomatosis in three Japanese patients from two unrelated families.

The autosomal recessively inherited cholesterol metabolic disease, cerebrotendinous xanthomatosis (CTX), is caused by mutations in the sterol 27-hydroxylase gene. Three Japanese CTX patients from two unrelated families were studied genetically. By DNA sequence analysis a novel mutation of A for G substitution at amino acid position 372 (CGG 372Arg to CAG 372Gln) was identified in one of the CTX families. The mutation was also found in two patients from the other family, with a compound heterozygous pattern of A for G substitution at amino acid position 441 (CGG 441Arg to CAG 441Gln). The latter mutation was the same as previously reported by our group (J. Lipid Res. 1994. 35: 1031-1039). As the two mutations changed the restriction enzyme sites, rapid screening methods were developed for the detection of the carriers. Transfection of the two mutant cDNAs into COS cells resulted in markedly reduced sterol 27-hydroxylase activity. These results indicate that the two mutations are responsible for the deficiency of the sterol 27-hydroxylase activity in these patients. The features of mutations identified till now in Japanese CTX patients are also reviewed.

Cholestanetriol 26-Monooxygenase↗
PubMed1997

Clonal versus polyclonal Epstein-Barr virus infection in nasopharyngeal carcinoma cell lines.

In most nasopharyngeal carcinoma (NPC) biopsy specimens, the Epstein-Barr virus (EBV), particularly in the terminal repeat region genomic structure, reveals a clonal pattern. To evaluate this phenomenon in vitro, we infected EBV-negative NPC cell lines, which express secretory component (SC) protein on their cell surface, with EBV particles. The viral particles were obtained either from a subcloned single cell or from the original B95-8 cell line. EBV infection was performed by incubating IgA anti-EBV and EBV particles with NPC cells and confirmed by direct in situ PCR hybridization. Southern blot analysis of EBV terminal repeat in EBV-infected NPC cell lines was performed using a Xhol 1.9-kb DNA fragment from the right terminus of the EBV genome as a probe. We found that all four NPC cell lines (ie, NPC-TWO1; 03, 04, and 06) expressed SC protein on their surfaces and could be infected by EBV through the EBV IgA-SC complex. Southern blot analysis in the single cell-subcloned B95-8 cell line showed a clonal EBV terminal repeat with a higher molecular size; whereas the original B95-8 line revealed the polyclonal EBV DNA pattern. A similar clonal EBV genomic pattern with lower molecular size was seen in all EBV-infected NPC cell lines. For comparison, six NPC biopsy specimens were also examined; of these, five showed a single band, and the remaining showed one major band and several lower molecular-sized bands. The EBV genomic DNA in the infected cells was shown to be an episomal form. We conclude, therefore, that a single (clonal) form of EBV genome can be obtained from a mixed population of epithelial tumor cells, even when they are infected by multiple virions with single or multiple form(s) of the EBV genomic pattern.

Animals↗
PubMed1997

An investigation of attitudes, beliefs and behaviour of leprosy patients, family members and PHC workers towards multidrug therapy in Yangzhou and Dongtai Districts of China.

To improve the operational efficiency of multidrug therapy (MDT) implementation in rural areas, an investigation into the attitudes, beliefs and behaviour of leprosy patients and their family members as well as primary health care (PHC) workers towards MDT was carried out in Yangzhou and Dongtai Districts of China. A sample of 370 leprosy patients, 594 family members and 730 PHC workers was interviewed or investigated individually using questionnaires. The results showed that: 1, the presently used MDT is acceptable to a wide range of patients although a small number of patients have various problems in their treatment; 2, the patients' habit in daily drug administration, their awareness of the risk of default and confidence in MDT have a positive influence in increasing drug compliance; and 3, the supervision and encouragement of family members to patients' treatment which is associated with their knowledge on MDT is also beneficial to patients' drug compliance. However, only half of the PHC workers had a basic knowledge of MDT and a desire to participate in MDT implementation, a finding which clearly calls for urgent attention and improvement. In order to ensure the effective implementation of MDT, there is a need to educate leprosy patients and their family members as well as PHC workers to establish the patients' correct awareness of MDT, obtain the family support and motivate the PHC workers.

Adult↗
PubMed1997

GB virus-C/hepatitis G virus infection in prostitutes: possible role of sexual transmission.

The modes of transmission of GB virus-C/hepatitis G virus (GBV-C/HGV) other than by blood transfusion are largely unknown. The prevalence of GBV-C/HGV viremia and the associated risk factors in 145 female prostitutes were examined. The seroprevalence of hepatitis B surface antigen (HBsAg), antibodies to hepatitis C virus (anti-HCV), and GBV-C/HGV RNA were 14%, 18%, and 11%, respectively. The demographic characteristics were similar between subjects with and without HBsAg. In contrast, those with HCV or GBV-C/HGV infection had practised longer as prostitutes and received blood transfusion more frequently. Moreover, the prevalence of GBV-C/HGV RNA and anti-HCV tended to increase in parallel with the duration of prostitution. These results suggest that like HCV, sexual transmission of GBV-C/HGV occurs and the risk increased with prolonged duration of exposure. The transmission efficiency between GBV-C/HGV and HCV appears to be similar.

Adult↗