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Biomedical subjects

L Wen

Publications and source records attributed to L Wen.

At least 109 records · Page 6Linked to original sources
PubMed1996

[The electron microscopic observation of the effect of monoclonal antibody on the form and structure of mutans streptococci OMZ176].

The effect of monoclonal antibody on the form and structure of Mutans Streptococci OMZ176 was studied. The result showed that a great number of Mutans Streptococci OMZ176 was agglutianated after treating with monoclonal antibody prepared by a cell wall protein antigen (molecular weight 220 kd) of Mutans Streptococci OMZ176. Bacterial cells were swollen obviously. The gap between cell wall and cytoplasmic was widened. The electronic density of cell plasm was greatly decreased.

Antibodies, Monoclonal↗
PubMed1996

[The epidemiological study on human cytomegalovirus infection of pregnant women and the maternal-fetal transmission in three Chinese metropolis].

OBJECTIVES: To analyze the state of human cytomegalovirus (HCMV) infection of pregnant women and the maternal-fetal transmission in three chinese metropolis, and to study the methods of early prenatal diagnosis for intrauterine infection. METHODS: Enzyme linked immunosorbent assay (ELISA) technique was employed to screen HCMV specific antibodies in 5,015 pregnant women of different trimesters. From this cohort study, 301 cases of active infection were selected to detect HCMV DNA by polymerase chain reaction (PCR) technique in their appendages of fetus, blood and urine of neonates, as well as breast milk. RESULTS: The overall HCMV infection rate was 88.93% in the three metropolis and they were 96.74% and 91.42% in Shenyang and Shanghai respectively, which were significantly higher than that (79.53%) in Wuhan. The active infection rate was 5.42% generally while they were 11.23% and 10.89% in Wuhan and Shenyang respectively, which were significantly higher than that in Shanghai. In addition, the active infection rate of women with history of abnormal pregnancy was significantly higher than that was of the control group (14.59% vs 3.70%). By PCR technique, the detective rate of HCMV DNA were 16.00% in chroionic villi of early pregnancy and 35.33% in amniotic fluid of mid-trimester, which were not significantly different from these in umbilical blood, placentea at delivery and neonatal blood. CONCLUSIONS: In China, the HCMV infection rates during pregnancy varied in different regions. A majority of women at children bearing age had HCMV infection before pregnancies; the yertical transmission frequently occurs from the actively infected mother. ELISA combined with PCR techniques is a valuable method for early prenatal diagnosis of HCMV congenital infection.

Adult↗
PubMed1995

Validity of the three-column theory of thoracolumbar fractures. A biomechanic investigation.

STUDY DESIGN: This study validated the three-column theory of fractures by correlating the multidirectional instabilities and the vertebral injuries to each of the three columns, using a biomechanic trauma model. OBJECTIVES: The objective was to validate the three-column theory as applied to the thoracolumbar fractures. SUMMARY OF BACKGROUND DATA: The widely used three-column theory of fractures for classification and evaluation was based on retrospective analysis of radiographs. No biomechanic study, using realistic spinal fractures and multidirectional instability measurements, was available. METHODS: Using 16 fresh cadaveric thoracolumbar human spine specimens, two groups of burst fractures were produced by either simple axial compression or flexion-compression, using a high-speed trauma model. Multidirectional flexibility was measured before and after the trauma, thus quantifying the instability of the burst fracture. Computed tomography scans were taken after the fracture, and a newly developed injury scoring scheme quantified the injuries to the anterior, middle, and posterior columns. Statistical correlations were obtained between the flexibility parameters and injuries to each of the three columns. RESULTS: In the axial compression group, the middle column injury, compared with the other two columns, showed the highest correlations to eight of the nine flexibility parameters (average R2 = 0.77). In the flexion-compression group, again the middle column injury showed the highest correlations to eight of the nine flexibility parameters (average R2 = 0.85). CONCLUSIONS: The results of this study supported the three-column theory of the thoracolumbar fractures and bolstered the concept of the middle column being the primary determinant of mechanical stability of this region of the spine.

Adult↗
PubMed1995

Changing the inhibitory specificity and function of Cucurbita maxima trypsin inhibitor-V by site-directed mutagenesis.

Cucurbita maxima trypsin inhibitor-V (CMTI-V) is also a specific inhibitor of human blood coagulation factor beta-factor XIIa. A recombinant version of CMTI-V has allowed probing of roles of individual amino acid residues including the reactive site residue, lysine (P1), by site-directed mutagenesis. The K44R showed at least a 5-fold increase in inhibitory activity toward human beta-factor XIIa, while there was no change toward bovine trypsin. This result demonstrates that beta-factor-XIIa prefers an arginine residue over lysine residue, while trypsin is non-specific to lysine or arginine in its binding pocket. On the other hand, the specificity of CMTI-V could be changed from trypsin to chymotrypsin inhibition by mutation of the P1 residue to either leucine or methionine (K44L or K44M).

Animals↗
PubMed1995

Genetic variation in VP7 gene of human rotavirus serotype 2 (G2 type) isolated in Japan, China, and Pakistan.

Sequence analysis of the gene encoding the major neutralization glycoprotein (VP7) was performed on sixteen human isolates of serotype 2 of rotavirus in Japan, China, and Pakistan and their genetic variations were examined. Comparative studies of their nucleotide and deduced amino acid sequences between the sixteen isolates and the HU5 strain revealed an overall homology of more than 94%. A higher degree of homology in nucleotides was observed among the sixteen isolates than between HU5 and the isolates. A total of thirteen amino acid residues frequently converted to another amino acid. Out of the thirteen, five amino acid residues belonging to the major neutralizing epitope regions (C, E, and F in this communication) converted frequently. From the amino acid sequences three subtypes, subtype 1, subtype 2, and intermediate, were suggested to be classified as previously reported for serotype 1 (Xin et al, Virology, 1993, 197: 813-816).

Amino Acid Sequence↗
PubMed1995

[Uteroplacental blood flow monitoring by color Doppler flow imaging in pregnancy induced hypertension].

The uteroplacental blood flow was monitored using color Doppler flow imaging (CDFI) in 31 cases of pregnancy induced hypertension (PIH) and 71 cases of normal pregnancy. At the same time the values of serum estriol (E3), human placental lactogen (hPL), thromboxane (TXB2), 6-KP and TXB2/6-KP ratio were measured. The results showed that time average velocity (TAV) and volume of blood flow (Q) of uterine and umbilical arteries in PIH cases were much lower than those in normal pregnant women and fetuses (P < 0.05). After treatment with magnesium sulfate and qingxintong there was a marked improvement in placental blood flow. TAV and Q of uterine and umbilical arteries was also increased (P < 0.05). In PIH cases the E3 and hPL levels were much lower, while the ratio of TXB2/6-KP was significantly higher than that in normal pregnancy. Using CDFI to observe the velocity and volume of uteroplacental blood flow can monitor the blood supply of uterus and placenta. It is a valuable predictive index of fetal and placental function.

Acetophenones↗
PubMed1995

Dynamic canal encroachment during thoracolumbar burst fractures.

In the burst fractures seen clinically, often poor correlation exists between the neurological deficit and the canal encroachment measured on post-trauma radiographic images. The purpose of the present study was to determine whether the dynamic canal encroachment during the trauma is greater than the static canal encroachment posttrauma. We successfully produced burst fractures in nine of 15 fresh human cadaveric thoracolumbar spine specimens (T11-L1). The specimens were incrementally impacted in a high-speed trauma apparatus until fracture occurred. During the trauma, dynamic canal encroachments were measured using three specially designed transducers placed in the canal at the levels of the superior end-plates of the T12 and L1 and the T12/L1 disk. After the trauma, residual static spinal canal encroachments were measured from the radiographs of the specimens that were prepared with 1.6-mm diameter steel balls lining the canal in the midsagittal plane. We found that the average canal diameter was 16.6 +/- 1.3 mm and the static canal encroachment was 18.0% of the canal diameter. The corresponding dynamic canal encroachment was 33.3%. Thus, the dynamic canal encroachment was 85% more than the static measurement. The clinical significance of this study lies in providing awareness to the clinician that the dynamic canal encroachment is significantly greater than the static canal encroachment seen on posttrauma radiographs or computed tomography scans. The finding may also explain the clinical observation of poor correlation between the canal encroachment measured radiographically and the neurological deficit.

Adult↗
PubMed1995

Experimental studies of the effect of Forskolin on the lowering of intraocular pressure.

PURPOSE: To determine the effect of domestic Forskolin on lowering of intraocular pressure (IOP) in rabbits. METHODS: Measure the normal IOP and ocular hypertension by water load in rabbits using Perkins tonometer. Measure the adenylate cyclase (AC) activity by Ho & Sutherland's method. RESULTS: The results show that Forskolin significantly lowered the normal IOP of rabbits and blocked the ocular hypertension induced by water load in rabbits (P < 0.01). The maximum decrease value of 2%, 1% and 0.5% of the Forskolin was 0.59, 0.36 and 0.19 kPa (1kPa = 7.5 mmHg), which showed the noticeable dose-effect relationship. Topical ocular application of Forskolin lowered IOP in half an hour, reached to a peak in 2-3 hours and remained significantly for 10 hours. The pupillary diameter did not change when IOP was reduced. The Forskolin had potent stimulative properties to AC. The greater the ability of the Forskolin to stimulate AC, the stronger the effect of IOP lowering. CONCLUSIONS: The Forskolin had the effect on lowering the IOP of rabbits. The mechanism of IOP reduction by Forskolin is related to its AC activation.

Adenylyl Cyclases↗
PubMed1994

Lymphocyte proliferation in mice congenitally deficient in T-cell receptor alpha beta + cells.

In mice and humans, T cells are characterized on the basis of T-cell receptor (TcR) expression and divided into the major TcR alpha beta + and minor TcR gamma delta + populations. TcR alpha beta + cells are considered to be the primary regulators of the immune response, whereas the function of TcR gamma delta + cells is unclear. Mice congenitally deficient in TcR alpha beta-expressing cells provide an ideal model for analyzing the independent in vivo function of TcR gamma delta + cells in the absence of TcR alpha beta + cells. Here we report that lymphoid organs in TcR alpha mutant mice undergo substantial enlargement after being challenged by environmental antigens. This organ expansion can be attributed in part to increases in the relative proportions and absolute numbers of TcR gamma delta + cells, but an expansion of the recently described TcR beta + alpha - population also has a role. The expansion of the TcR gamma delta + population is polyclonal, as evidenced by the usage of multiple gamma and delta variable chain segments. Furthermore, a substantial proportion of the cells appears to be activated and these activated cells express surface activation markers. The results clearly demonstrate that TcR gamma delta + cells proliferate independently in response to a broad spectrum of challenges. Moreover, since the expansion of the lymphoid tissues and the TcR gamma delta + cell population is excessive relative to that seen in wild-type animals, one role of TcR alpha beta + cells is directly or indirectly to limit the responses of the other lymphoid components.

Animals↗
PubMed1994

Immunoglobulin synthesis and generalized autoimmunity in mice congenitally deficient in alpha beta(+) T cells.

Through cognate B-cell-T-cell interactions and provision of cytokines, CD4+ T-cell antigen receptor (TCR) alpha beta+ T cells regulate immunoglobulin isotype synthesis. Murine IgG1 and IgE secretion is therefore substantially T-cell-dependent, whereas IgM and IgG3 secretion is not. Here we report that in the absence of alpha beta T cells, B cells expand, differentiate and secrete copious amounts of antibodies of 'T-dependent' isotypes. Moreover, the antibodies are reactive towards self-antigens, as in patients with systemic lupus erythematosus, so autoantibodies of 'T-dependent' type can develop without the help of CD4+ alpha beta T cells. This phenotype is not evident in mice or humans that are congenitally deficient in specific alpha beta T-cell functions, but bears comparison with B-cell hyperactivity and autoimmunity in transplant rejection and in immunodeficiencies such as AIDS.

Animals↗
PubMed1994

Estimates of trace element intakes in Chinese farmers.

Epidemiologic data on the average daily human dietary intake of the trace elements nickel, cadmium, molybdenum and silicon are scarce, worldwide, primarily because foods consumed vary widely over days and seasons. Available full year food allocation records for farmers in rural areas of China provide an unique opportunity to estimate dietary trace elements. In 1988, we measured the concentration of zinc, copper, iron, cadmium, nickel, molybdenum, silicon and selenium in different foods by using food samples collected from 232 villages (distributed among 21 communes). These measurements, combined with the food consumption information from existing food allocation records in each commune for an entire year, allowed us to estimate the average daily consumption of these trace elements by Chinese farmers. With one exception (an association of zinc and esophageal cancer), the variation of dietary trace elements did not show any association with mortality from several common diseases. The estimates for some of the dietary trace elements from some subpopulations were either less or more than current recommendations. No increases in mortality were found, however, from diseases normally associated with either dietary deficiencies or excesses of these elements.

Adult↗
PubMed1994

Differences in immune recognition of cytochrome P4502D6 by liver kidney microsomal (LKM) antibody in autoimmune hepatitis and chronic hepatitis C virus infection.

LKM-1 antibody, which characterizes a subtype of autoimmune hepatitis (AIH), is also found in some patients with chronic hepatitis C virus (HCV) infection. It has been suggested that HCV initiates autoimmunity through molecular mimicry, because there is partial identity between HCV and cytochrome P4502D6 (CYP2D6), the putative target of LKM-1. Whether CYP2D6 is the target of LKM-1 in HCV-related liver disease, however, is controversial. To clarify this issue, we have studied by phage plaque assay and Western blot the reactivity to recombinant CYP2D6, isolated from a human liver cDNA library, in 55 patients with LKM-1, 18 (14 females, median age 12 years) anti-HCV-negative, with classical AIH, and 37 (27 females, median age 52 years) anti-HCV-positive. Reactivity to CYP2D6 was found in 72% of the anti-HCV-negative, but only in 27% of the anti-HCV-positive patients (P < 0.001), although immunofluorescence LKM-1 titres were similar in the two groups. In addition, to investigate whether the antibody responsible for the LKM-1 fluorescent pattern also reacts with CYP2D6, we have determined the specificity of LKM-1 antibodies present in the supernatant of lymphoblastoid B cell lines obtained from two patients with LKM-1-positive AIH. An oligo/monoclonal antibody thus generated gave both the typical fluorescent pattern and reacted with CYP2D6. Our results show that whilst antibodies producing the characteristic LKM-1 fluorescent pattern can react with CYP2D6, not all LKM-1-positive sera do so, particularly if obtained from patients with chronic HCV infection. This suggests that LKM-1 in HCV infection recognizes epitopes or antigens different from those targeted in AIH.

Adolescent↗
PubMed1994

T cell clones generated from patients with type 1 diabetes using interleukin-2 proliferate to human islet antigens.

T lymphocytes are implicated in the pathogenesis of Type 1 (insulin dependent) diabetes. Activated T lymphocytes expressing IL-2 receptors are found at increased levels in the peripheral blood in the prediabetic period, at diagnosis and for several months after the onset of the disease, but their role in the pathogenesis of the disease is not known. We have used co-culture of peripheral blood lymphocytes with IL-2 alone to selectively generate T cell clones from the in vivo activated T cell population, and examined the phenotype and antigen specificity of the clones derived. From 3 patients with newly-diagnosed Type 1 diabetes 184 clones were generated, the majority of which (39%) were CD4+TCR alpha beta+, whilst 31% were CD8+TCR alpha beta+. From 2 healthy control subjects 90 clones were obtained, of which 62% were CD4+TCR alpha beta+ and 33% were CD8+TCR alpha beta+. Antigen specificity was examined in 46 clones from the patients and 44 from the control subjects in proliferation assays, using as antigens homogenate of human islets of Langerhans, human islet membrane preparation and human liver membrane preparation. Three clones (all CD4+TCR alpha beta+) from the patients, but none from the control subjects, proliferated in a dose dependent fashion in response to stimulation with human islet homogenate presented by autologous APCs, but to neither of the other autoantigen preparations. Our results demonstrate that a relatively high proportion (7%) of T lymphocytes activated in vivo recognise human islet antigens, indicating that they may have a role in the pathogenesis of the disease.

Adult↗
PubMed1994

Analysis of the peripheral T-cell receptor V beta repertoire in newly diagnosed patients with type I diabetes.

Type I diabetes is an autoimmune disease characterised by a marked activation of peripheral T cells around the time of clinical diagnosis. Studies of T-cell antigen receptor V beta (TCRBV) gene usage in type I diabetes have been conflicting. Using a semi-quantitative polymerase chain reaction technique and flow cytometry we have investigated the TCRBV gene usage of 13 newly diagnosed patients with type I diabetes and 11 normal healthy controls. No preferential TCRBV gene usage was found between patients and controls even after matching for HLA-DR3 and/or -DR4. In addition, no significant differences in TCRBV gene usage were found between sequential samples taken over a period of up to 7 months following diagnosis. These results suggest that the TCR repertoire of these patients is heterogeneous and it is unlikely that a single 'pathogenic' T-cell clone is dominant at the clinical onset of the disease.

Adult↗
PubMed1993

Chemical synthesis, molecular cloning, overexpression, and site-directed mutagenesis of the gene coding for pumpkin (Curcubita maxima) trypsin inhibitor CMTI-V.

The gene encoding for a pumpkin (Curcubita maxima) trypsin inhibitor CMTI-V was synthesized chemically. The synthetic gene was prepared from four overlapping oligonucleotides by overlapping extension. The synthetic gene was amplified by polymerase chain reaction, cloned into a T7 expression vector and expressed in Escherichia coli as a fusion protein. The clone, namely 70-1, encoded a fusion protein containing 7 amino acid residues of the N-terminus of the bacterial protein rho 10 and the entire 68 residues of CMTI-V. The wild-type fusion protein constituted approximately 15% of the total bacterial protein mass and was purified to homogeneity in a single step by antibody affinity chromatography. The wild-type fusion protein possesses inhibitory activity toward trypsin and beta-Factor XIIa, but to a lesser extent when compared to the natural CMTI-V. A mutant, T43A, in which threonine at position 43 (P2 position) was replaced by alanine, was constructed. This mutant showed considerably lower specific inhibitory activity toward both trypsin and beta-Factor XIIa.

Amino Acid Sequence↗
PubMed1993

The human T cell receptor V beta repertoire of normal peripheral blood lymphocytes before and after mitogen stimulation.

Mitogen stimulation of T cells in vitro has been employed in the analysis of the T cell antigen receptor (TCR) repertoire and as a method of generating T cell lines and clones. It has been suspected for some time that mitogen stimulation may bias the repertoire. We have addressed this problem employing a semi-quantitative technique utilizing the polymerase chain reaction (PCR) and flow cytometry. Using this PCR method and a panel of primers to 22 V beta subgroups, the V beta repertoire of both unstimulated and phytohaemagglutinin (PHA)-stimulated peripheral T cells from eight healthy individuals was investigated. The samples were also analysed by flow cytometry using anti-V beta 2, V beta 5 and V beta 8 MoAbs. A significant increase in the expression of V beta 6, V beta 7.2 and V beta 10.1 was found in all eight samples of PHA-stimulated T cells compared with unstimulated T cells using the PCR method. In contrast, no differences were found between unstimulated and PHA-stimulated T cells by flow cytometry. These results question the validity of using mitogen-stimulated T cells to investigate TCR gene usage.

Base Sequence↗