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Biomedical subjects

L Wen

Publications and source records attributed to L Wen.

At least 37 records · Page 2Linked to original sources
PubMed2001

A preliminary clinical study of three-dimensional ultrasonography in prenatal diagnosis.

To evaluate the clinical value of three-dimensional ultrasonography (3DUS) in prenatal diagnosis, 134 pregnant women with high-risk factors in second and third trimester were examined by 3DUS. The results showed that 3DUS could provide more diagnostic information, exclude the abnormalities and enhance the confidence level of physician in 102 normal pregnant women. 3DUS was helpful in the diagnosis in 17 (60.7%) of 28 cases of fetal anomalies. However, 3DUS was not useful in evaluating intrauterine growth retardation in 4 cases. It is concluded that 3DUS is helpful in prenatal diagnosis.

Adult↗
PubMed2001

Three-dimensional ultrasonography in obstetrics: the clinical value.

To investigate the clinical value of three-dimensional ultrasonography (3DUS) in obstetrics, various 3DUS rendering methods including surface mode, transparent mode and multiplanar mode were employed to scan 30 fetuses in second and third trimester by using the transabdominal volume transducer. The results showed that surface mode could vividly demonstrate the surface morphologic features of the fetuses, as well as the stereo-shape and the spatial relationship among the surface structures. The face, limbs, umbilical cord and outer genitalia of the fetus could be well displayed by surface mode. Transparent mode could reveal the bony structures under the surface, such as ribs, vertebrae, crania, etc. The result was not affected by the sophisticated curvature of these bony structures and the success rate was up to 100%. When rendered by multiplanar mode, the region of interest (ROI) could be viewed from different directions. It should be concluded that 3DUS could serve as a supplement to two-dimensional ultrasonography (2DUS). 3DUS might play an important role in prenatal diagnosis and enhance the diagnostic confidence level of the physicians.

Female↗
PubMed2001

Computer simulation of the distribution of aluminum speciation in soil solutions in equilibrium with the mineral phase imogolite.

The speciation of aluminum (Al) is a critical issue when evaluating the environmental and biological significance of elevated Al concentrations in soil solutions caused by acidic precipitation. Numerous studies have revealed that, with increased concentrations of silica acid in soil, the activity of Al species in soil solutions is greatly modified by SiO(4)(2-). However, thus far there has been little thorough theoretical modeling of this subject. This paper reports a computer simulation of the distribution of Al speciation in soil solutions in equilibrium with the mineral phase imogolite based on a chemical equilibrium calculation. The unique characteristic associated with imogolite reported by previous researchers can be explained theoretically by the proposed model. The dissolved silica has a remarkable influence on Al speciation: increasing concentrations of silica acid may effectively inhibit the formation of polymeric alumino-hydroxo species, and, furthermore, detoxify Al toxicity to plants.

Aluminum↗
PubMed2001

Disulfide bond effects on protein stability: designed variants of Cucurbita maxima trypsin inhibitor-V.

Attempts to increase protein stability by insertion of novel disulfide bonds have not always been successful. According to the two current models, cross-links enhance stability mainly through denatured state effects. We have investigated the effects of removal and addition of disulfide cross-links, protein flexibility in the vicinity of a cross-link, and disulfide loop size on the stability of Cucurbita maxima trypsin inhibitor-V (CMTI-V; 7 kD) by differential scanning calorimetry. CMTI-V offers the advantage of a large, flexible, and solvent-exposed loop not involved in extensive intra-molecular interactions. We have uncovered a negative correlation between retention time in hydrophobic column chromatography, a measure of protein hydrophobicity, and melting temperature (T(m)), an indicator of native state stabilization, for CMTI-V and its variants. In conjunction with the complete set of thermodynamic parameters of denaturation, this has led to the following deductions: (1) In the less stable, disulfide-removed C3S/C48S (Delta Delta G(d)(50 degrees C) = -4 kcal/mole; Delta T(m) = -22 degrees C), the native state is destabilized more than the denatured state; this also applies to the less-stable CMTI-V* (Delta Delta G(d)(50 degrees C) = -3 kcal/mole; Delta T(m) = -11 degrees C), in which the disulfide-containing loop is opened by specific hydrolysis of the Lys(44)-Asp(45) peptide bond; (2) In the less stable, disulfide-inserted E38C/W54C (Delta Delta G(d)(50 degrees C) = -1 kcal/mole; Delta T(m) = +2 degrees C), the denatured state is more stabilized than the native state; and (3) In the more stable, disulfide-engineered V42C/R52C (Delta Delta G(d)(50 degrees C) = +1 kcal/mole; Delta T(m) = +17 degrees C), the native state is more stabilized than the denatured state. These results show that a cross-link stabilizes both native and denatured states, and differential stabilization of the two states causes either loss or gain in protein stability. Removal of hydrogen bonds in the same flexible region of CMTI-V resulted in less destabilization despite larger changes in the enthalpy and entropy of denaturation. The effect of a cross-link on the denatured state of CMTI-V was estimated directly by means of a four-state thermodynamic cycle consisting of native and denatured states of CMTI-V and CMTI-V*. Overall, the results show that an enthalpy-entropy compensation accompanies disulfide bond effects and protein stabilization is profoundly modulated by altered hydrophobicity of both native and denatured states, altered flexibility near the cross-link, and residual structure in the denatured state.

Circular Dichroism↗
PubMed2001

The regulatory role of DR4 in a spontaneous diabetes DQ8 transgenic model.

MHC class II molecules are critical determinants of genetic susceptibility to human type 1 diabetes. In patients, the most common haplotype contains the DRA1*0101-DRB1*0401 (DR4) and DQA1*0301-DQB1*0302 (DQ8) loci. To assess directly the relative roles of HLA-DQ8 and DR4 for diabetes development in vivo, we generated C57BL/6 transgenic mice that lack endogenous mouse MHC class II molecules but express HLA-DQ8 and/or DR4. Neither HLA-DQ nor HLA-DR transgenic mice developed insulitis or spontaneous diabetes. However, when they were crossed to transgenic mice (C57BL/6) expressing the B7.1 costimulatory molecules on pancreatic beta cells that do not normally develop diabetes, T cells from these double transgenic mice were no longer tolerant to islet autoantigens. The majority of DQ8/RIP-B7 mice developed spontaneous diabetes, whereas only 25% of DR4/RIP-B7 mice did so. Interestingly, when DQ8 and DR4 were coexpressed (DQ8DR4/RIP-B7), only 23% of these mice developed diabetes, an incidence indistinguishable from the DR4/RIP-B7 mice. T cells from both DR4/RIP-B7 and DQ8DR4/RIP-B7 mice, unlike those from DQ8/RIP-B7 mice, exhibited a Th2-like phenotype. Thus, the expression of DR4 appeared to downregulate DQ8-restricted autoreactive T cells in DQ8DR4/RIP-B7 mice. Our data suggest that although both DQ8 and DR4 can promote spontaneous diabetes in mice with a non-autoimmune-prone genetic background, the diabetogenic effect of the DQ8 allele is much greater, whereas DR4 expression downregulates the diabetogenic effect of DQ8, perhaps by enhancing Th2-like immune responses.

Animals↗
PubMed2001

Two-step cycle sequencing improves base ambiguities and signal dropouts in DNA sequencing reactions using energy-transfer-based fluorescent dye terminators.

The use of automated fluorescent DNA sequencer systems and PCR-based DNA sequencing methods plays an important role in the actual effort to improve the efficiency of large-scale DNA analysis. While dideoxy-terminators labeled with energy-transfer dyes (BigDyes) provide the most versatile method of automated DNA sequencing, premature terminations result in a substantially reduced reading length of the DNA sequence. Premature terminations are usually evidenced by base ambiguities and are often accompanied by diminished signal intensity from that point on in the sequence. I studied a two-step protocol for Taq cycle sequencing using the ABI BigDye terminator for reducing premature terminations in DNA sequences. I demonstrate that combining the annealing step with the extension step at one temperature (60 degrees C) reduces premature terminations in DNA sequences that regularly contain premature terminations when the three temperature steps are used. This modification significantly increases the number of accurately read bases in DNA sequences.

Base Sequence↗
PubMed2001

Pediatric autoimmune liver diseases: the molecular basis of humoral and cellular immunity.

Pediatric autoimmune liver disease is mainly represented by two similar liver disorders: autoimmune hepatitis (AIH) and autoimmune sclerosing cholangitis (ASC), both characterized by hypergammalobulinemia, interface hepatitis and the presence of a wide range of circulating autoantibodies. Although similar features are seen in AIH and inflammatory bowel disease, histological biliary changes are more common in ASC. In addition to their role as diagnostic markers, autoantibodies, such as anti-extractable nuclear antigen (ENA) antibodies and liver kidney microsomal antibody type 1 (LKM1) may be involved directly in inducing aggressive liver diseases. Although the cellular immune response in pediatric autoimmune liver disease has been less intensively investigated than humoral immunity, the importance of antigen specific T cells has been explored. Both alphabeta and gammadelta T cells derived from either peripheral blood and liver biopsies have highly heterogeneous TCR gene usage and cytolytic activity has been demonstrated. There have been attempts to seek triggers of liver autoimmunity and several sequences shared in common between autoantigens and hepatotropic viruses, namely hepatitis B, C and cytomegalovirus have been identified. The presence of cross-reactivity between homologous sequences, especially between HCV and cytochromes, supports the possibility that molecular mimicry plays a role in the induction of autoantibodies and autoreactive cytotoxic T cells.

Amino Acid Sequence↗
PubMed2001

Report from the 1st International NOD Mouse T-Cell Workshop and the follow-up mini-workshop.

A workshop on autoreactive T-cell responses in NOD mice was held to optimize autoreactive T-cell detection methodologies. Using different proliferation assay protocols, 1 of the 11 participating laboratories detected spontaneous T-cell responses to GAD(524-543) and insulin(9-23) in their NOD mice. Two other laboratories were able to detect autoreactive responses when using enzyme-linked immunospot assay (ELISPOT) and enzyme-linked immunosorbent assay (ELISA) analysis of cytokines in culture supernatants, suggesting that these assays provided greater sensitivity. To address the divergent findings, a follow-up mini-workshop tested NOD mice from four different colonies side-by-side for T-cell proliferative responses to an expanded panel of autoantigens, using the protocol that had enabled detection of responses in the 1st International NOD Mouse T-Cell Workshop. Under these assay conditions, 16 of 16 NOD mice displayed proliferative responses to whole GAD65, 13 of 16 to GAD(524-543), 9 of 16 to GAD(217-236), 7 of 16 to insulin(9-23), and 5 of 16 to HSP277. Thus, spontaneous proliferative T-cell responses can be consistently detected to some beta-cell autoantigens and peptides thereof. Overall, the results suggest that more sensitive assays (e.g., ELISPOT, ELISA analysis of cytokines in supernatants, or tetramer staining) may be preferred for the detection of autoreactive T-cells.

Animals↗
PubMed2001

[Preparation and identification of activity of antiplatelet-derived growth factor receptor beta subunit hammerhead ribozyme in vitro].

OBJECTIVE: To study the preparation and cleavage activity of ribozyme directed against platelet-derived growth factor (PDGF) receptor beta subunit gene transcript in vitro. METHODS: PDGF receptor B subunit gene fragments were cloned into T-vector under the control of T7 promotor. 32P-labeled PDGF receptor beta subunit transcripts as target-RNAs were transcribed in vitro and purified by PAGE. Ribozyme gene designed by computer targeting the extracellular domain was cloned into vector P1.5 between 5'-cis ribozyme and 3'-cis ribozyme. 32P-labeled ribozyme transcripts was gel-purified, incubated with target-RNAs at different conditions and autoradiographed after denaturing gel-electrophoresis. RESULTS: The preparation of ribozyme was correct. It was active at 37 degrees C. The optimal temperature was 50 degrees C, Km=13,20 nm, Kcat=0.28 min-1. The cleavage efficiency was up to 78.3%. CONCLUSIONS: Ribozyme prepared in vitro possesses specific catalytic activity.

Animals↗
PubMed2001

[Effect of calcium hydroxide on human pulp cell intracellular calcium ion in vitro].

OBJECTIVE: To investigate the influence of calcium hydroxide to intracellular calcium ion of human pulp cells in vitro. METHODS: The sixth generation of human pulp cells were maintained in RPMI 1640 medium supplemented with Fluo-3 probe and Ca (OH)2 for restimulation. The intracellular calcium ion concentration was detected by laser confocal microscope. RESULTS: The intracellular calcium ion level in Ca (OH)2 pretreatment group increased after Ca (OH)2 stimulation, while it didn't response to Ca (OH)2 stimulus in group without Ca (OH)2, CaCl2 or NaHCO4 pretreatment. CONCLUSION: It is important to pretreat the pulp cells with Ca(OH)2 in order to increase the intracellular calcium.

Calcium↗
PubMed2001

[Study on the genetic variations of the major neutralization antigen VP7 of group A rotavirus type G1 in China].

OBJECTIVE: To study the genetic variations of the major neutralization antigen VP7 of group A rotavirus, type G1 in China. METHODS: Twenty-three isolates derived from seven cities (Beijing, Shenyang, Xinxiang, Shanghai, Shenzhen, Guangzhou and Chongqing) during the period of 1988-1998 were analyzed for the VP7 cDNA sequences. RESULTS: An obvious homology was observed in amino acid sequences of VP7 in the 23 isolates. Compared with the standard strain Wa, the variations were found at the position of aa 41, 49, 57, 65, 68, 74, 94, 97, 147, 170, 217, 218, 268, 281 and 291, respectively, and all of these were located in the variable region(VR)3,4,5,7,8 as well as in the C-terminal of the peptide. There seemed to be no remarkable divergence among the samples collected from different cities and all of them shared the same genetic lineage with the strain Jpn-417, though there might be one or two amino acid substitutions as time passed. When detected simultaneously with ELISA using G1 serotype-specific monoclonal antibody, the location of amino acid 91 was found presumably related to the neutralization epitope in VP7 of the type G1. Variations at some position may be resulted in the change of electropherotype. CONCLUSIONS: The results indicated that the recent isolates with representative genetic and antigenic features should be used to develop effective vaccines, and the antigenic variations should be monitored periodically.

Amino Acid Sequence↗
PubMed2001

[Investigation of group A rotavirus infection in several cities in China and prevalence of VP7 serotype].

OBJECTIVE: To study the prevalence of Group A rotavirus infection in China. METHODS: 374 samples from infants with diarrhea were collected from six cities (Beijing, Shenyang, Xinxiang, Shanghai, Shenzhen and Guangzhou) in autumn and winters of 1997 and/or 1998. The incidence of rotavirus infection and the prevalence of the four dominant serotypes G1, G2, G3, G4(VP7 serotype) were detected by PAGE and RT-PCR. RESULTS: Of the 374 samples detected, 181 were rotavirus positive. The positive rate was 48.4%, ranging from 32%-63% in different cities. The positive rates between 1997 and 1998 in Beijing and Shanghai were similar. Serotyped by RT-PCR method based on VP7 sequence, the positive rates of type G1, G2, G3 and G4 was 89.5%, 6.1%, 2.8% and 0, respectively. Two cases were found being coinfected with G1 and G2, and one case was confirmed to be infected with G9 by cDNA sequence analysis. There was a little difference in prevalence of G type rotavirus infection among samples from different cities and different years. CONCLUSION: The results indicated that rotavirus was the most important etiologic agent in this country, and the predominant serotypes were G1, G2 and G3.

Antigens, Viral↗
PubMed2000

In vivo evidence for the contribution of human histocompatibility leukocyte antigen (HLA)-DQ molecules to the development of diabetes.

Although DQA1*0301/DQB1*0302 is the human histocompatibility leukocyte antigen (HLA) class II gene most commonly associated with human type 1 diabetes, direct in vivo experimental evidence for its diabetogenic role is lacking. Therefore, we generated C57BL/6 transgenic mice that bear this molecule and do not express mouse major histocompatibility complex (MHC) class II molecules (DQ8(+)/mII(-)). They did not develop insulitis or spontaneous diabetes. However, when DQ8(+)/mII(-) mice were bred with C57BL/6 mice expressing costimulatory molecule B7-1 on beta cells (which normally do not develop diabetes), 81% of the DQ8(+)/mII(-)/B7-1(+) mice developed spontaneous diabetes. The diabetes was accompanied by severe insulitis composed of both T cells (CD4(+) and CD8(+)) and B cells. T cells from the diabetic mice secreted large amounts of interferon gamma, but not interleukin 4, in response to DQ8(+) islets and the putative islet autoantigens, insulin and glutamic acid decarboxylase (GAD). Diabetes could also be adoptively transferred to irradiated nondiabetic DQ8(+)/mII(-)/B7-1(+) mice. In striking contrast, none of the transgenic mice in which the diabetes protective allele (DQA1*0103/DQB1*0601, DQ6 for short) was substituted for mouse MHC class II molecules but remained for the expression of B7-1 on pancreatic beta cells (DQ6(+)/mII(-)/B7-1(+)) developed diabetes. Only 7% of DQ(-)/mII(-)/B7-1(+) mice developed diabetes at an older age, and none of the DQ(-)/mII(+)/B7-1(+) mice or DQ8(+)/mII(+)/B7-1(+) mice developed diabetes. In conclusion, substitution of HLA-DQA1*0301/DQB1*0302, but not HLA-DQA1*0103/DQB1*0601, for murine MHC class II provokes autoimmune diabetes in non-diabetes-prone rat insulin promoter (RIP).B7-1 C57BL/6 mice. Our data provide direct in vivo evidence for the diabetogenic effect of this human MHC class II molecule and a unique "humanized" animal model of spontaneous diabetes.

Animals↗
PubMed2000

Reversal of the vasoconstrictor step of hyperacute xenogeneic rejection of the liver by endothelin antagonists.

The role of endothelin in the initial vasoconstrictor step of hyperacute xenogeneic rejection was investigated. Isolated rat livers were perfused in recirculation. Perfusion with human sera provided an ex vivo model of hyperacute rejection in a discordant combination. Perfusion of 10% xenogeneic serum induced a marked (70%) and sustained reduction of the liver flow and induced the release of endothelin into the perfusion medium. In contrast, perfusion of 10% allogeneic serum or of 10% decomplemented human serum induced a weak (25%) and transient reduction of the liver flow and induced the release of minimal amounts of endothelin. The simultaneous administration of BQ 123 and BQ 788, the respective antagonists of ET(A) and ET(B) endothelin receptors, or that of bosentan, a mixed ET(A)/ET(B) antagonist, antagonized the vasoconstrictor effect of 10% xenogeneic human serum, as well as that of 10(-9) M endothelin-1. The vasoconstrictor effects of xenogeneic serum on liver circulation are, at least partly, mediated through the release of endothelin by the graft.

Animals↗
PubMed2000

Triamcinolone acetonide modulates permeability and intercellular adhesion molecule-1 (ICAM-1) expression of the ECV304 cell line: implications for macular degeneration.

Whilst animal studies and a pilot clinical trial suggest that intravitreal triamcinolone acetonide (TA) may be useful in the treatment of age-related macular degeneration (AMD), its mode of action remains to be fully elucidated. The present study has investigated the capacity of TA to modulate the expression of adhesion molecules and permeability using a human epithelial cell line (ECV304) as a model of the outer blood-retinal barrier (BRB). The influence of TA on the expression of ICAM-1 and MHC-I was studied on resting and phorbol myristate acetate (PMA)- or interferon-gamma (IFN-gamma)- and/or tumour necrosis factor-alpha (TNF-alpha)-activated cells using flow cytometry and immunocytochemistry. Additionally, ECV304 cells were grown to confluence in uncoated Transwell chambers; transepithelial resistance (TER) across resting and PMA-activated cells was monitored. TA significantly decreased the paracellular permeability of ECV304 cells and down-regulated ICAM-1 expression, consistent with immunocytochemical observations. PMA-induced permeability changes were dose-dependent and TA decreased permeability of both resting and PMA-activated monolayers. MHC-I expression by ECV304 cells however, was not significantly affected by TA treatment. The modulation of TER and ICAM-1 expression in vitro correlate with clinical observations, suggesting re-establishment of the BRB and down-regulation of inflammatory markers are the principal effects of intravitreal TA in vivo. The results further indicate that TA has the potential to influence cellular permeability, including the barrier function of the retinal pigment epithelium (RPE) in AMD-affected retinae.

Animals↗
PubMed2000

Suppression of humoral immunization against encapsulated xenogeneic hepatocytes and prolongation of their function by 2-week cyclosporine treatment in the rat.

BACKGROUND: Xenogeneic liver transplantation may induce immune reactions not only against the grafted liver but also against the proteins that it synthesizes. We investigated whether 2-week cyclosporine treatment could suppress immunization and improve graft function in a xenogeneic hepatocyte transplantation model. METHODS: Free or encapsulated human hepatoma cells (HepG2) were cocultured for 28 days with splenocytes from Lewis rats or implanted for 60 days into the peritoneum of Lewis rats. RESULTS: Anti-HepG2 and antialbumin antibodies were detected in the supernatants of rat splenocytes that were cocultured with HepG2 cells and in the serum of rats that had undergone transplantation with HepG2 cells. Cyclosporine suppressed this antibody production both in vitro and in vivo. Human alpha-GST blood levels, which reflect hepatocyte injury, were low in cyclosporine-treated animals but high when encapsulated HepG2 cells were transplanted without cyclosporine therapy. Western blots revealed human albumin from day 3 to day 60 in the serum of rats treated with cyclosporine, but not after day 30 in untreated rats. CONCLUSIONS: Xenogeneic hepatocytes induce a humoral response that impairs their viability and function. A 2-week course of cyclosporine suppresses this immune response and improves graft function for up to 60 days.

Animals↗
PubMed2000

Fatty acids enhanced tubermycin production by Pseudomonas strain 2HS.

A new microbial isolate, Pseudomonas 2HS, produced trace amounts of a greenish-yellow pigment when grown aerobically in a 1% yeast extract medium at 30 degrees C and shaken at 250 rpm for 5 days. In contrast, cells produced more greenish-yellow pigment (2.16 mg/15 ml culture) when grown in the presence of 0.5% 12-hydroxyoctadecanoic acid (w/v). The greenish-yellow pigment was identified as phenazine-1-carboxylic acid (tubermycin B), and the Pseudomonas 2HS was identified as P. aeruginosa 2HS. This is the first report that 12-hydroxyoctadecanoic, ricinoleic and other fatty acids can enhance the production of phenazine-1-carboxylic acid by a Pseudomonas species.

Animals↗