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Biomedical subjects

X Chen

Publications and source records attributed to X Chen.

At least 1,171 records · Page 65Linked to original sources
PubMed1997

[Relationship between human parvovirus B19 infection and spontaneous abortion].

OBJECTIVE: To determine whether there is a relationship between parvovirus B19 infection and spontaneous abortion. METHODS: 105 embryo tissues from spontaneous abortions of unknown cause during 1994-1995 were studied using nested polymerase chain reaction (PCR) assay for parvovirus B19 DNA. As controls 40 fetal tissues were also examined. Among which, 20 were collected from induced abortions, and the others were stillbirths. The positive specimens underwent further study for TORCH infections. RESULTS: 26 (24.5%) were B19 DNA positive in the case group and 2 (5.0%) in the control group. The difference was significant (P < 0.05). Among 26 positive specimens, 5 had cytomegalovirus (CMV) infection as well as 2 had both CMV and herpes simplex virus (RSV) infections. CONCLUSIONS: Parvovirus B19 infection may be an important pathogen for spontaneous abortion, and it is suggested to investigate parvovirus B19 infection among pregnant women in China.

Abortion, Spontaneous↗
PubMed1997

[Trauma and tumor: a report of 14 cases].

In the present article, we report 14 cases of patients with different tumors, injured or died after a traumatic episode. The relation between trauma and tumor, and the associated problems in forensic medicine are discussed.

Adolescent↗
PubMed1997

[Effects of glycated protein on the expression of plasminogen activator inhibitor-1 of cultured human mesangial cells].

OBJECTIVE: To investigate whether nonenzymatic glycated end products (AGEs) have effects on the expression and bioactivity of plasminogen activator inhibitor-1 (PAI-1), one of the seripin proteinases, which lead to extracellular matrix (ECM) degradation in cultured human mesangial cells. METHODS: Human mesangial cells (HMC) were cultured. Cell proliferation, fibronectin production, mRNA expression and bioactivity of PAI-1 were determined after exposure to AGE-BSA for 24 hours and 48 hours in vitro. RESULTS: HMC stimulated by AGE-BSA exhibited inhibition in HMC proliferation, increase in fibronectin production, and PAI-1 bioactivity. These changes were pronounced with prolongation of experimental time. PAI-1 mRNA expression increased significantly at 24 hr (0.45% +/- 0.06% vs 0.65% +/- 0.08%, P < 0.05), however more marked increase of PAI-1 mRNA expression at 48 hr (0.51 +/- 0.08% vs 0.92 +/- 0.10%, P < 0.01). CONCLUSIONS: Increase of mRNA expression and bioactivity of PAI-1 induced by AGEs decreased ECM degradation and play an important role in the pathogenesis of ECM accumulation and glomerulosclerosis.

Cell Division↗
PubMed1997

[Prognostic factors of dermatomyositis: analysis of 119 cases].

In order to know the prognosis of dermatomyositis, 119 patients with dermatomyositis were investigated from June to September 1995 by Shanghai Medical Cooperation Center on Dermatomyositis. Ten prognostic factors were studied with Lifereg Procedure multiple factor analysis. The results showed that 2 and 5-year survival rates were 75.3% and 53.2% respectively. The most common cause of death was lung infection and then was malignant tumor. Unfavorable prognostic factors were old age, malignant tumor, interstitial lung disease, dysphagia, cardiac involvement, fever, failure of remission and steroid therapy alone. The survival curve showed that mortality rate was high in the first three years, less between three and seven years and none after seven years. The results showed that dermatomyositis is a disease with poor prognosis. Patients with dermatomyositis can be adversely affected by many factors and should be treated regularly with steroid and immunosuppresive drugs as early as possible.

Adolescent↗
PubMed1997

[Effects of methylprednisolone (MPS) on induction of apoptosis and expression of interleukin-1 beta-converting enzyme (ICE) in the kidneys of MRL-LPR/LPR mice].

MPS pulse therapy is quite effective for the treatment of lupus nephritis. At present, no research work has been reported on the relationship between MPS therapy and apoptosis and ICE expression in kidneys with lupus nephritis. We investigated the effects of MPS on the number of apoptotic cells and expression of ICE mRNA in the kidneys of fourmonth-old MRL-lpr/lpr mice, by means of image analysis system, RT-PCR and Northern blot. The results showed that in MPS group, the number of apoptotic cells in glomerular mesangium increased significantly, as compared with that of a control group (P < 0.05). Besides, the number of apoptotic cells in both the peri-tubule cells and peri-vascular infiltrating cells was also higher in MPS group than in the control group (both P < 0.01). Furthermore, higher expression of ICE mRNA was found in the treated group than in the control group. Our results suggest that MPS may induce both apoptosis and ICE mRNA expression in kidneys with nephritis, implying that apoptosis may be involved in the outcome of lupus nephritis treated with MPS.

Animals↗
PubMed1997

[Changes of NMDA receptor gene expression in infection brain injury induced by Bordetella pertussis in rats].

N-methyl-D-aspartate receptors (NMDAR) in cerebral cortexes of rat brain injury induced by Bordetella pertussis (Bp) were measured by methods of Northern blot analysis and [3H] MK-801 radioligand-receptor binding to study changes and effects of NMDAR1 of gene expression in the infection brain injury. The affinity (Kd) of NMDAR in Bp group was significantly decreased [30.5 +/- 3.0 nmol.L-1 (Bp), 43.1 +/- 4.2 nmol.L-1 (NS), P < 0.05], but expression of NMDAR1 mRNA and binding site density (Bmax) of NMDAR observed no significant differences between the experimental and the control group (P > 0.05), respectively. The results suggest that NMDAR1 was activated with high affinity functionally, but no changes in binding site density and transcriptional expression of NMDAR1 occured in the infection brain injury.

Animals↗
PubMed1997

[Delayed brain injury induced by Bordetella pertussis in rats].

To induced new model of delayed infection brain injury, we divided randomly 40 adult male Sprague-Dawley rats into four groups: bordetella pertussis (BP) groups, and normal sailine (NS) groups in 4 h (n = 10) and 24 h (n = 10), respectively, injected BP at 0.2 ml.kg-1 which contained the bacilli in 10.8 x 10(9).ml-1 into the rat left internal carotid artery of BP groups, and injected at the equal volume as control in the same way into NS groups. The water content (WC), Evans blue content (EB), cations of sodium, potassium, calcium in the brain tissues were measured and the morphologic changes in the hippocampal CA1 were detected by electron microscopy. These results were shown as follows: the left hemisphere of BP group in 4 h was characterized by the brain edema which predominated in swollen, necrotic astroglial cells, endothelial cells, and insignificant increase of contents of sodium, calcium and decrease of potassium; BP group in 24 h was characterized by dark cells, the brain edema also existed in astroglial cells. These results indicate that a delayed infection brain injury model is performed successfully by injection with BP into the left internal carotid artery of rats. The model is characterized by the features of delayed neuronal death and mixed type brain edema.

Animals↗
PubMed1997

[Simultaneous determination of eight kinds of conjunct bile acids in human bile by R-HPLC].

A method for the simultaneous determination of eight kinds of conjunct bile acids in human bile was developed by HPLC. They were separated on a YWG-C18 (3 microns) column at 30 degrees C, with methanol/water (65/35, V/V, pH3.0) as mobile phase, and detection wavelength at UV 210 nm. The linear ranges were 50-1,000 microns.ml-1, the recoveries were 91.2%-108.6%. The biles of 30 cases with cholelithiasis cholecystolithiasis and 20 cases without gallstone were detected by HPLC. The results showed that the constitution of bile acids was different between patients with cholelithiasis cholecystolithiasis and patients without gallstone.

Bile↗
PubMed1996

Structure-function correlations of the insulin-linked polymorphic region.

The insulin minisatellite of the insulin-linked polymorphic region (ILPR), a 14 base-pairs long tandem repeat of: 5'-ACAGGGGTGTGGGG-3' 3'-TGTCCCCACACCCC-5', is located 363 base-pairs upstream of the human insulin gene. A locus for insulin-dependent diabetes mellitus (IDDM) has been mapped to the ILPR. It has been shown that the ILPR is polymorphic in length and this length polymorphism is also related to the transcriptional activity of the insulin gene and the susceptibility to IDDM. Here, we attempt to decipher the role of the ILPR structure in length polymorphism and transcriptional regulation. We show by gel electrophoresis, circular dichroism (CD) and one and two-dimensional nuclear magnetic resonance spectroscopy (1D/2D NMR) that the G-rich strand of the ILPR adopts an intramolecularly folded hairpin G-quartet structure. A detailed analysis of 1D/2D NMR data of d(G4TGTG4) and d(G4TGTG4ACAG4TGTG4) enables us to define the nature of chainfolding, the stacking interaction of the G-tetrads in the stem, and the interactions of the bases in the loops. d(G4TGTG4ACAG4TGTG4) happens to be the smallest unit of the G-rich strand that can form the intramolecular hairpin G-quartet structure. For long ILPR sequences, several such hairpin G-quartet structures can be linked in space. Indeed, by an in vitro replication assay, we show the presence of such multiple hairpin G-quartet structures for the G-rich strand of the ILPR of repeat length 6. This observation suggests that the formation of multiple hairpin G-quartets may explain slippage during replication and the observed length polymorphism. From our high resolution structure, we are able to identify a set of interactions that are critical for the structure and stability of the hairpin G-quartet. Single or double mutations in the ILPR that destabilize these interactions also lower the transcriptional activity of the insulin gene. Therefore, the hairpin G-quartet structure of the ILPR has a direct correlation with the transcriptional activity of the human insulin gene.

DNA↗
PubMed1996

Mutations in the hepatocyte nuclear factor-1alpha gene in maturity-onset diabetes of the young (MODY3)

The disease non-insulin-dependent (type 2) diabetes mellitus (NIDDM) is characterized by abnormally high blood glucose resulting from a relative deficiency of insulin. It affects about 2% of the world's population and treatment of diabetes and its complications are an increasing health-care burden. Genetic factors are important in the aetiology of NIDDM, and linkage studies are starting to localize some of the genes that influence the development of this disorder. Maturity-onset diabetes of the young (MODY), a single-gene disorder responsible for 2-5% of NIDDM, is characterized by autosomal dominant inheritance and an age of onset of 25 years or younger. MODY genes have been localized to chromosomes 7, 12 and 20 (refs 5, 7, 8) and clinical studies indicate that mutations in these genes are associated with abnormal patterns of glucose-stimulated insulin secretion. The gene on chromosome 7 (MODY2) encodes the glycolytic enzyme glucokinases which plays a key role in generating the metabolic signal for insulin secretion and in integrating hepatic glucose uptake. Here we show that subjects with the MODY3-form of NIDDM have mutations in the gene encoding hepatocyte nuclear factor-1alpha (HNF-1alpha, which is encoded by the gene TCF1). HNF-1alpha is a transcription factor that helps in the tissue-specific regulation of the expression of several liver genes and also functions as a weak transactivator of the rat insulin-I gene.

Animals↗
PubMed1996

Gene delivery to skeletal muscle results in sustained expression and systemic delivery of a therapeutic protein.

Somatic gene therapy has been proposed as a means to achieve systemic delivery of therapeutic proteins. However, there is limited evidence that current methods of gene delivery can practically achieve this goal. In this study, we demonstrate that, following a single intramuscular administration of a recombinant adeno-associated virus (rAAV) vector containing the beta-galactosidase (AAV-lacZ) gene into adult BALB/c mice, protein expression was detected in myofibers for at least 32 weeks. A single intramuscular administration of an AAV vector containing a gene for human erythropoietin (AAV-Epo) into mice resulted in dose-dependent secretion of erythropoietin and corresponding increases in red blood cell production that persisted for up to 40 weeks. Primary human myotubes transduced in vitro with the AAV-Epo vector also showed dose-dependent production of Epo. These results demonstrate that rAAV vectors are able to transduce skeletal muscle and are capable of achieving sustained expression and systemic delivery of a therapeutic protein following a single intramuscular administration. Gene therapy using AAV vectors may provide a practical strategy for the treatment of inherited and acquired protein deficiencies.

Animals↗
PubMed1996

A significant fraction of functional SecA is permanently embedded in the membrane. SecA cycling on and off the membrane is not essential during protein translocation.

SecA has been suggested to cycle on and off the cytoplasmic membrane of Escherichia coli during protein translocation. We have reconstituted 35S-SecA onto SecA-depleted membrane vesicles and followed the fate of the membrane-associated 35S-SecA during protein translocation. Some 35S-SecA was released from the membranes in a translocation-independent manner. However, a significant fraction of 35S-SecA remained on the membranes even after incubation with excess SecA. This fraction of 35S-SecA was shown to be integrated into the membrane and was active in protein translocation, indicating that SecA cycling on and off membrane is not required for protein translocation. Proteolysis experiments did not support the model of SecA insertion and deinsertion during protein translocation; instead, a major 48-kDa domain was found persistently embedded in the membrane regardless of translocation status. Thus, in addition to catalyzing ATP hydrolysis, certain domains of SecA probably play an important structural role in the translocation machinery, perhaps forming part of the protein-conducting channels.

Adenosine Triphosphatases↗
PubMed1996

Very low rates of hip fracture in Beijing, People's Republic of China the Beijing Osteoporosis Project.

One third of the world's hip fractures are said to occur in Asia, mostly in China. However, there have as yet been no validated studies of hip fracture rates in China. The authors estimated the incidence of hip fractures in Beijing, People's Republic of China, and took several steps to validate the estimates. All 76 Beijing hospitals reported all 1988-1992 admissions that had been coded as 820 (hip fracture) or 821 (other femoral fracture) according to the International Classification of Diseases, Ninth Revision. The authors then compared a random sample of the reports with original medical records, and discovered that 70% of intertrochanteric hip fractures had been miscoded as "other femoral fractures." The authors retrained all hospital staffs to provide corrected reports. Revised reports missed only 13% of the hip fracture cases recorded in operating room logs of 11 randomly selected hospitals. To validate hospital-based estimates of hip fracture rates, the authors interviewed a random sample of 2,113 Beijing women aged 50 years or more (97% response rate); all but 4% of past fractures and all seven hip fractures had been treated in hospitals. Finally, the authors surveyed the 27 hospitals in the counties surrounding Beijing. No Beijing residents had been treated for hip fracture outside of the city. Based on the 1990 China census, age-standardized rates of hip fracture (per 100,000) in Beijing-87 for women, 97 for men-were much lower than those seen in Hong Kong in 1985 (353 for women, 181 for men) or in US Caucasians (510-559 for women, 174-207 for men). From 1988 to 1992, the rates in Beijing increased 34% in women and 33% in men. The authors conclude that hip fracture rates in Beijing are among the lowest in the world but may be rising rapidly.

Adult↗
PubMed1996

Erythroid Krüppel-like factor (EKLF) contains a multifunctional transcriptional activation domain important for inter- and intramolecular interactions.

Erythroid Krüppel-like factor (EKLF) is a red cell-restricted transcriptional activator that plays a dominant role in establishing high levels of beta-globin gene expression during erythroid ontogeny. Although its DNA binding domain belongs to the well-studied class of Krüppel-like zinc fingers, its proline-rich activation region has not been thoroughly examined. We have analyzed this region by monitoring the functional effects of its mutagenesis upon EKLF activity in vivo and in vitro. First, using co-transfection assays, we find that the transactivation region contains discrete stimulatory and inhibitory subdomains. Second, in vitro binding assays indicate that the inhibitory domain exerts its effect in cis by interfering with DNA binding. Third, in vivo competition assays demonstrate that EKLF interacts with a positive-acting cellular factor, and that the domain responsible for this trans interaction lies within a 40 amino acid sequence that is coincident with the EKLF minimal transactivation domain. Finally, site-directed mutagenesis of this domain implies that conformation and/or phosphorylation status of its central core may be critical for such interactions. These results point towards post-translational steric and/or allosteric control of EKLF function that may be important not just for its DNA binding ability, but also for its potential to interact with other proteins that fully establish the correct stereospecific array leading to efficient switching of beta-globin transcription during development.

Amino Acid Sequence↗
PubMed1996

A transcriptional partner for MAD proteins in TGF-beta signalling.

The transforming-growth-factor-beta (TGF-beta) superfamily is critical for establishing mesoderm during early embryogenesis in Xenopus. The transcriptional activation of Mix.2, an immediate-early response gene specific to activin-like members of the TGF-beta superfamily, is associated with the rapid appearance of a site-specific DNA-binding activity that recognizes a fifty-base-pair regulatory element known as ARE in the Mix.2 promoter. Cloning of the site-specific DNA-binding component of this activity revealed it to be a new winged-helix transcription factor and a direct target for signalling by the TGF-beta superfamily. XMAD2, a recently identified TGF-beta signal transducer, forms a complex with the transcription factor in an activin-dependent fashion to generate an activated ARE-binding complex. A model is proposed to explain how TGF-beta superfamily signals might regulate the expression of specific genes in the early embryo.

Activins↗
PubMed1996

Development of microsatellite markers and characterization of simple sequence length polymorphism (SSLP) in rice (Oryza sativa L.).

Microsatellite markers containing simple sequence repeats (SSR) are a valuable tool for genetic analysis. Our objective is to augment the existing RFLP map of rice with simple sequence length polymorphisms (SSLP). In this study, we describe 20 new microsatellite markers that have been assigned to positions along the rice chromosomes, characterized for their allelic diversity in cultivated and wild rice, and tested for amplification in distantly related species. Our results indicate that the genomic distribution of microsatellites in rice appears to be random, with no obvious bias for, or clustering in particular regions, that mapping results are identical in intersubspecific and interspecific populations, and that amplification in wild relatives of Oryza sativa is reliable in species most closely related to cultivated rice but becomes less successful as the genetic distance increases. Sequence analysis of SSLP alleles in three related indica varieties demonstrated the clustering of complex arrays of SSR motifs in a single 300-bp region with independent variation in each. Two microsatellite markers amplified multiple loci that were mapped onto independent rice chromosomes, suggesting the presence of duplicated regions within the rice genome. The availability of increasing numbers of mapped SSLP markers can be expected to increase the power and resolution of genome analysis in rice.

Alleles↗