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Biomedical subjects

X R Chen

Publications and source records attributed to X R Chen.

At least 19 recordsLinked to original sources
PubMed2004

Bacterial diversity in Malan ice core from the Tibetan Plateau.

Three ice core samples were collected from the Malan ice core drilled from the Tibetan Plateau, and three 16S rDNA clone libraries by direct amplification from the ice-melted water were established. Ninety-four clones containing bacterial 16S rDNA inserts were selected. According to restriction fragment-length polymorphism analysis, 11 clones were unique in the library from which they were obtained and used for partial sequence and phylogenetic analysis, and compared with 8 reported sequences from the same ice core at depth 70 m. Differences among the samples were apparent in clone libraries. The phylotypes were dominated by the Proteobacteria group, Acinetobacter sp. and Cytophaga-Flavobacterium-Bacteroides (CFB) group. They accounted for 92.5% (Proteobacteria), 100% (Acinetobacter sp.), 34.4% (CFB) and 100% (beta-Proteobacteria) in the clone libraries from the samples at ice depths 35, 64, 70, and 82 m, respectively. The Acinetobacter sp. was only found in the deposition at ice depth 82 m and closely clustered with gamma-Proteobateria. Two members (Malan A-21 and 101) of alpha-Proteobacteria from the sample of 35 m and two (Malan B-26 and 48) of beta-Proteobacteria of 64 m were loosely clustered (< 95% similarity) with known bacteria, represented new genera in ice bacteria.

Bacteria↗
PubMed2003

Bioaccumulation of nickel from aqueous solutions by genetically engineered Escherichia coli.

This study constructed a genetically engineered Escherichia coli JM109 which simultaneously expressed nickel transport system and metallothionein to remove and recover Ni(2+) from aqueous solution. Bioaccumulation process was rapid and followed linearized Langmuir isotherm. A more than six-fold increase of Ni(2+) binding capacity was obtained by genetically engineered E. coli cells compared with original host E. coli cells. A pH assay showed genetically engineered E. coli cells accumulated Ni(2+) effectively over a broad range of pH (4-10). The presence of 1000 mg/L Na(+) and Ca(2+), or 50mg/L Cd(2+) or Pb(2+) did not have a significant effect on Ni(2+) bioaccumulation, while Mg(2+), Hg(2+) and Cu(2+) posed a severe adverse influence on Ni(2+) uptake by genetically engineered E. coli. Furthermore, genetically engineered E. coli cells did not require extra nutrients for Ni(2+) bioaccumulation.

Biodegradation, Environmental↗
PubMed2001

[Analysis of monoclonal protein in 72 cases of multiple myeloma].

Serum and urinary monoclonal proteins (M protein) were measured in 72 cases of multiple myeloma (MM) using rate nephelometry. In IgG and IgA types of MM, the level of immunoglobulin (Ig) corresponding to the malignant isotype was significantly higher and that of Ig uncorresponding to the malignant isotype lower than the normal level. The light chain corresponding to the malignant isotype in serum was increased and the light chain uncorresponding to that in serum was decreased either kappa-IgG, IgA types or lambda-IgG, IgA types. Either kappa-LC or lambda-LC type of MM, the serum light chain corresponding to the malignant isotype was in the normal range and uncorresponding to that was decreased, and the corresponding light chain in urine was significantly elevated. Kappa/lambda ratio in serum and urine was all significantly abnormal in IgG, IgA, and LC types of MM. Our data suggest that any quota among kappa light chain > 20 g.L-1 or < 5 g.L-1, lambda light chain > 10 g.L-1 or < 2 g.L-1 in serum and kappa/lambda ratio > 5 or < 0.75 in serum and urine has an important value for diagnosing MM.

Adult↗
PubMed2001

Autocrine regulation of norepinephrine transporter expression.

The norepinephrine transporter (NET) is a neurotransmitter scavenger and site of drug action in noradrenergic neurons. The aim of this study was to identify mechanisms that regulate NET expression during the development of quail (q) sympathetic neuroblasts, which develop from neural crest stem cells. Neurotrophin-3 (NT-3) and transforming growth factor beta1 (TGF-beta1) cause an increase of qNET mRNA levels in neural crest cells. When combined, the growth factors are additive in increasing qNET mRNA levels. Both NT-3 and TGF-beta1 are synthesized by neural crest cells. Onset of NET expression precedes the onset of neural crest stem cell emigration from the neural tube. In older embryos, qNET is expressed by several crest-derived and noncrest tissues. The data show that qNET expression in presumptive sympathetic neurons is initiated early in embryonic development by growth factors that are produced by neural crest cells themselves. Moreover, the results support our previous observations that norepinephrine transport contributes to the regulation of the differentiation of neural crest stem cells into sympathetic neurons.

Animals↗
PubMed1998

Tissue distribution, regulation and intracellular localization of murine CD1 molecules.

CD1 molecules are MHC-unlinked class Ib molecules consisting of classical (human CD 1a-c) and non-classical subsets (human CD1d and murine CD1). The characterization of non-classical subsets of CD1 is limited due to the lack of reagents. In this study, we have generated two new anti-mouse CD1 monoclonal antibodies, 3H3 and 5C6, by immunization of hamsters with purified CD1 protein. These antibodies recognize CD1-transfected cells and have no reactivity to cells isolated from CD1-/- mice. Both antibodies precipitate the 52 kDa heavy chain and 12 kDa beta2m from thymocytes and splenocytes by radio-immunoprecipitation. Deglycosylation of CD1 reduces molecular mass of the heavy chain by 7.5 kDa, which can be detected by 3H3 but not 5C6. 3H3 and 5C6 detect surface CD1 expression on cells from the thymus, spleen, lymph node and bone marrow, but not on intestinal epithelial cells. Developmentally, CD1 is expressed on thymocytes prior to TCR rearrangement and remains constant throughout thymic development. CD1 is expressed early in the fetal liver (day 14) and remains expressed in hepatocytes postnatally. These data support evidence of a role for CD1 in the selection and/or expansion of NK1- T cells of both thymic origin and extrathymic origin. Unlike classical class I molecules, murine CD1 levels are not affected by IFN-gamma, but like human CD1b can be up-regulated by IL-4 and GM-CSF although only moderately. Similar to human CD1b, murine CD1 is found by immunofluorescence microscopy on the cell surface, and in various intracellular vesicles, including early and late endosomes. Localization in endocytic compartments indicates that murine CD1 may be capable of binding endocytosed antigens.

Animals↗
PubMed1998

Osteoarthrosis of the temporomandibular joint induced by intra-articular injection of lactate dehydrogenase: an experimental study in adult rabbits.

OBJECTIVE: The purpose of this study was to establish an animal model of osteoarthrosis in the temporomandibular joint (TMJOA) by injecting lactate dehydrogenase (LDH) into the maxillary compartments of TMJs in adult rabbits. METHODS: Adult New Zealand white rabbits were randomly divided into four groups (A through D) of five animals each. The A and B groups were used as a control. The maxillary compartments of the C and D group (TMJs) were injected with 0.1 mL of LDH in two different concentrations. The TMJ samples were analyzed histologically and with a scanning electron microscope four different times after injection. RESULTS: The animals that had been injected with LDH at two different concentrations showed similar results. The TMJs had changes typical of OA in early to moderate stages. No pathologic changes could be found in the TMJs of the control groups. CONCLUSIONS: The results suggest that LDH may be of use in establishing an animal model of TMJOA.

Animals↗
PubMed1998

[Mismatch repair in MNNG-induced genetically unstable monkey kidney vero cell].

Gel retardation analysis and in vitro DNA mismatch repair system were used to examine whether there were mismatch repair deficiency in MNNG-induced genetically unstable vero cell, which was manifested by a delayed and highly increased rate of non-targeted mutation. A mismatch binding protein which could selectively bind to G.T mispair in DNA was identified in its whole-cell extracts. It was also identified that G.T mispair could be specifically and effectively corrected into G.C pair in its nuclear extracts. Compared with normal vero cell, there were no functional deficiency of the above mismatch repair mechanisms. So it could be excluded the possibility that the functional deficiency of mismatch binding protein or G.T mismatch repair pathway participated in the induction of genetic instability in vero cell by MNNG.

Animals↗
PubMed1998

Sequence analysis of a fragment of rOmpA gene of several isolates of spotted fever group rickettsiae from China.

The nucleotide sequence of rOmpA gene fragment of three Chinese isolates of spotted fever group rickettsiae (SFGR) (BJ-90, Ha-91 and HLJ-054) was determined. The obtained nucleotide and putative amino acid sequences were compared with those of another Chinese SFGR isolate (HL-93) and several prototype SFGR strains. This comparison showed that the isolates BJ-90 and Ha-91 are closely related to each other and R. sibirica but different from the isolates HLJ-054 and HL-93. We assume that with exception of the isolates HLJ-054 and HL-93 that represent new, unique members of SFGR, the isolates BJ-90 and Ha-91 are closely related to R. sibirica, one of the prototype SFGR strains.

Amino Acid Sequence↗
PubMed1997

Rapid phosphorylation of Ets-2 accompanies mitogen-activated protein kinase activation and the induction of heparin-binding epidermal growth factor gene expression by oncogenic Raf-1.

Heparin-binding epidermal growth factor (HB-EGF) gene transcription is rapidly activated in NIH 3T3 cells transformed by oncogenic Ras and Raf and mediates the autocrine activation of the c-Jun N-terminal kinases (JNKs) observed in these cells. A 1.7-kb fragment of the promoter of the murine HB-EGF gene linked to a luciferase reporter was strongly induced following activation of deltaRaf-1:ER, a conditionally active form of oncogenic human Raf-1. Promoter activation by deltaRaf-1:ER required a composite AP-1/Ets transcription factor binding site located between bp -974 and -988 upstream of the translation initiation site. In vivo genomic footprinting indicated that the basal level of occupancy of this composite AP-1/Ets element increased following deltaRaf-1:ER activation. Cotransfection of Ets-2 and p44 mitogen-activated protein (MAP) kinase expression vectors strongly potentiated HB-EGF promoter activation in response to deltaRaf-1:ER. Potentiated activation required both p44 MAP kinase catalytic activity and threonine 72 in the Pointed domain of Ets-2. Biochemical assays demonstrated the ability of the p42 and p44 MAP kinases to phosphorylate Ets-2 on threonine 72. Importantly, in intact cells, the kinetics of phosphorylation of Ets-2 on this residue closely mirror the activation of the p42 and p44 MAP kinases and the observed onset of HB-EGF gene transcription following deltaRaf-1:ER activation. These data firmly establish Ets-2 as a direct target of the Raf-MEK-MAP kinase signaling pathway and strongly implicate Ets-2 in the regulation of HB-EGF gene expression.

3T3 Cells↗
PubMed1996

The correlation between the loss of chromosome 14q with histologic tumor grade, pathologic stage, and outcome of patients with nonpapillary renal cell carcinoma.

BACKGROUND: Conventional pathologic classifications of human renal cell carcinoma (RCC) give little insight into oncogenesis and little assistance in predicting the clinical behavior of this disease. Identification of specific genetic alterations involved in the development of RCC using fluorescence in situ hybridization (FISH) however, may help provide foundations for classification, prognosis, and clinical management of the patients. METHODS: Archival, paraffin embedded tissue sections from 30 human non-papillary RCCs were examined with a dual color FISH technique for loss of chromosomes 3p and 14q. Telomeric DNA probes from 3p or 14q and an internal ploidy control probe, centromeric probe of chromosome 2, were applied directly to the tumor sections. The correlations between loss of 3p or 14q, and tumor ploidy, with tumor grade, pathologic stage, and patient outcome were assessed. RESULTS: Ninety percent of the patients (27) lost chromosome 3p, and 36.7% of the patients (11) had chromosome 14q deletions. The loss of 3p in the samples tested was unrelated to patient age, gender, outcome, tumor stage, or histologic grade. However, the deletion of 14q was significantly correlated with higher stage (P = 0.01), histologic grade (P = 0.01), and patient outcome (P < 10(-4)). CONCLUSION: The close correlation of 14q loss with higher stage, higher histologic grade, and poorer outcome for patients with nonpapillary RCC indicates that it may be a promising prognostic marker.

Adult↗
PubMed1996

Stereotactic Gamma thalamotomy for the treatment of parkinsonism.

From September 1994 to June 1995, eight patients with intractable parkinsonism underwent gamma thalamotomy in our hospital. All of these patients were male, with an average age of 59.3 years. The duration of the disease from initial diagnosis was 2-10 years (mean 6.8 years). All had failed or had serious side effects with antiparkinsonian medicine. Seven cases had tremor-dominant symptoms, while the other had mainly rigidity. Six cases had bilateral symptoms. Computed tomography or magnetic resonance imaging (MRI) was undertaken prior to treatment in all cases to exclude focal brain lesions. Stereotactic MRI was taken with the Leksell frame in place and both T1- and T2-weighted images were obtained. The targets were located in the area of Vim/Voa/Vop based on the Schaltenbrand atlas. In seven cases, two plugged 4-mm-collimator shots were used. The maximum dose was 160 Gy in six cases and 180 Gy in one case. In another case, a single 4-mm-collimator shot was used, and a maximum dose of 160 Gy was delivered to the target center. The border of the internal capsule was outside the 20-30% isodose line. We intended the 50% isodose line to have an oval-shaped region with the use of two shots and should correspond to the shape of Vim. Follow-up data were available for six patients (mean: 4.5 months, range: 2-9 months). Tremor disappeared in three cases and improved in the other three. In one of these six cases, the tremor disappeared just 3 days after gamma thalamotomy. Rigidity improved in four of these six cases. In only one patient, treated with a maximum dose of 180 Gy, was there any contralateral limb weakness, which developed 3 months after treatment and has been recovering gradually. Follow-up MRI T2-weighted images in this case showed that the diameter of the lesion was larger than intended and there was a region of diffuse edema in the thalamus and upper brain stem. No other complications occurred in this series.

Adult↗
PubMed1996

Avoiding serious complications in laparoscopic cholecystectomy--lessons learned from an experience of 2428 cases.

Over a three-and-a-half year period, we performed 2428 cases of laparoscopic cholecystectomy (LC) and encountered 11 cases of serious procedure-related complications, including bile duct injuries in 4 patients, postoperative bleeding requiring laparotomy and haemostasis in 3 patients, bile leakage from the cystic duct stump, jejunal injury related to puncture, intraoperative injury to the duodenum and subdiaphragmatic abscess in 1 patient each respectively. Six patients required re-hospitalisation including 2 patients with pancreatitis, 1 patient with Ascaris cholangitis, 1 patient with residual stone of the common bile duct (CBD) after laparoscopic CBD exploration, 1 patient with a stone in the CBD after LC, and 1 patient with bile leakage from the cystic duct stump and peritonitis. Of the 2428 patients treated, there was only 1 operative mortality. This patient developed frequent episodes of supraventricular tachycardia. She was found to have pnuemonia on the 21st postoperative day and she died. Apart from this, 1 other patient was found to have primary cancer of the liver 1 month after LC. Based on our experience, we think that LC is safe for patients with benign disease of the gallbladder.

Adolescent↗
PubMed1995

Extensive amplification of bcr/abl fusion genes clustered on three marker chromosomes in human leukemic cell line K-562.

Using fluorescence in situ hybridization (FISH), we were able to demonstrate 22-24-fold amplification of the bcr/abl fusion gene in the human leukemic cell line K-562. About 60% of the amplified sequences are localized to a large acrocentric marker chromosome, with another 30% clustered on a small acrocentric chromosome. In addition to these two masked Ph chromosomes, the remaining bcr/abl fusion genes are located on a der(2) distal to band q33. G- and C-banding analysis revealed similar unique banding patterns in both masked Ph chromosomes and suggests that amplification occurred by tandem duplication of the bcr/abl fusion site. Because the number of bcr/abl fusion genes may be increasing over time, it is critical that researchers using K-562 cells should be aware of this extensive amplification.

Chromosome Mapping↗
PubMed1994

[Laparoscopic cholecystectomy performed in 235 cases of cholecystitis with impacted gallstones].

During the past 2 years, 235 cases of cholecystitis with impacted gallstones were treated with laparoscopic technique. There were 221 chronic cases and 14 acute cases accounting altogether for 15.19% of a total of 1475 patients undergoing laparoscopic cholecystectomy during the same period. As a result, 9 of these patients were converted to open surgery. Severe adhesion around the gallbladder or/and in the Calot triangle in 7, acute impacted gallstone, gallbladder necrosis along with obscure anatomy in the calot triangle in 1, and gallstone impacted at the junction of the common hepatic and cystic duct in 1 were observed. Conversion rate was 3.8%. Postoperative bile leakage developed in 2 cases and healed spontaneously. There were no intraperitoneal sepsis and perioperative death in our patients. The diagnosis, classification, and management for acute or chronic impacted gallstone are discussed.

Adult↗
PubMed1994

In vitro radiation-induced neoplastic progression of low-grade uroepithelial tumors.

Recent interest has focused on the identification of molecular genetic mechanisms in multistep neoplastic transformation. In vitro exposure of simian virus 40 (SV40)-immortalized human uroepithelial cells (SV-HUC) that are environmentally relevant to bladder carcinogens has been shown to produce tumorigenic transformation, as assessed by the ability of cells exposed to a carcinogen to form xenograph tumors with heterogeneous cancer phenotypes ranging from very aggressive, invasive high-grade carcinomas to superficial low-grade indolent tumors. In addition, exposure of a low-grade indolent tumor generated in the SV-HUC system, MC-T11, to the same carcinogens results in neoplastic progression as assessed by the production of high-grade aggressive cancers. In the present study, we show neoplastic progression of MC-T11 after in vitro exposure to a single dose of 6 Gy X rays. In addition, we show that the chromosome deletions, including losses of 4q, 11p, 13q and 18, observed in these radiation-induced tumors are similar to those observed in carcinogen-induced tumors, thus supporting the hypothesis that the experimental cell system, not the transforming agent, dictates the genetic losses required for tumorigenic transformation and progression.

Animals↗
PubMed1993

[Laparoscopic cholecystectomy for benign gallbladder diseases].

From Sept. 1991 through Sept. 1992, 700 patients underwent laparoscopic cholecystectomy (LC), among them 171 were male and 529 were female with age ranging from 18 to 77, and 238 of them were overweighed. There were 35 cases of gallbladder polypi, 657, chronic calculous cholecystitis, 8 acute cholecystitis, with 13 cases having had previous upper abdominal surgeries. Intraoperative transcystic duct cholangiography were carried out in 10 cases and choledocholithiasis was confirmed in 5 of them. Exploring the CBD laparoscopically was done in 2.14 cases were converted to open surgery (2.6%). Twenty-five patients had postoperative complications including injuries to the extrahepatic bile duct and bleeding requiring laparotomic hemostasis in 3 and 2, respectively, with 1 patient dying of cardiac arrhythmia.

Adolescent↗
PubMed1993

[Efficacy of ivermectin for control of microfilaremia recurring after treatment with diethylcarbamazine: immunological observation].

We compared the effect of a single dose of ivermectin (100 micrograms/kg) with that of a standard course of diethylcarbamazine (DEC) (6 mg/kg) on several parameters of the host's antifilarial immune response in 60 patients with bancroftian filariasis enrolled in a double-blind drug trial. All participants had measurable serum levels of antifilarial antibodies and parasite antigens. Drug-induced clearance of microfilaremia was associated with a temporary increase in HC11 antigenemia and a decrease in serum levels of antibodies to soluble filarial antigens. Antigenemia progressively declined in patients who remained a microfilaremic after treatment, but declined and then rose in persons with recurrent microfilaremia. Treatment triggered a sustained increase in serum levels of IL-1, IL-6, TNF alpha and IFN gamma in all patients. Although Ivermectin and DEC are believed to exert their antiparasite activity via different mechanisms, the same pattern of serological changes was observed in patients treated with either drug.

Animals↗