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Biomedical subjects

J Chen

Publications and source records attributed to J Chen.

At least 1,081 records · Page 60Linked to original sources
PubMed2000

[mRNA expression of hyaluronan synthase in the endolymphatic sac cells of guinea pigs].

OBJECTIVE: To detect the mRNA expression of hyaluronan synthase in the endolymphatic sac cells of guinea pigs. METHODS: After consulting gene bank, we analyzed conservative sequence of hyaluronan synthases in different species, detected the mRNA expression of hyaluronan synthase in the endolymphatic sac cells of guinea pigs with oligonucleotide probe by hybridization in situ. RESULTS: mRNA of hyaluronan synthase was strongly expressed in some epithelial cells of endolymphatic sac, coupled with negative expression in negative control groups. CONCLUSION: It confirms that endolymphatic sac cells can synthesize hyaluronan.

Animals↗
PubMed2000

[Changes of p16 gene, cyclin D1 gene, and pRb protein in human pancreatic adenocarcinoma cell lines].

OBJECTIVE: To investigate the abnormalities of the relative factors of pRb-p16 cell regulatory pathway in pancreatic adenocarcinoma. METHODS: Five strains of human pancreatic adenocarcinoma cell lines were analysed by PCR and single-strand conformation polymorphism (SSCP) for homozygous deletion and mutation of the p16 gene, respectively. The gene amplification of cyclin D1 was detected by Southern blot analysis and the protein expression of pRb gene was examined by Western blot analysis. RESULTS: Homozygous deletion of exon 1 were found in two cell lines and no mutation was found within exon 1 and exon 2 in five cell lines. Cyclin D1 gene amplification was observed in one cell line and all of the five cell lines showed hyper-phosphorylated pRb protein. CONCLUSION: These findings have demonstrated that there are abnormalities of pRb-p16 regulatory pathway in pancreatic adenocarcinoma cell lines, revealing the alteration of the p16 and cyclin D1 genes.

Adenocarcinoma↗
PubMed2000

[Role of nitric oxide in excitotoxicity and memory impairment induced by kainic acid].

OBJECTIVE: The role of nitric oxide (NO) in excitotoxicity of kainic acid (KA) in the brain was investigated. METHODS: Adult female rats were bilaterally intra-caudate nucleus injected with KA. The nitric oxide synthase (NOS) was determined by measuring NO2- concentration produced from homogenized brain tissue in the enzyme response system at three time point after surgery. Another groups of rats were daily administrated (i.p.) L-NAME(10 mg/kg) or 7-NI(25 mg/kg) at 2nd to 6th day after intra-caudate KA injection. Behavioral tests for learning and memory were started at 10th day after surgery. RESULTS: NOS activity in caudate nucleus remained unchanged in 6-8 hours after surgery. It increased significantly in 3 days and slightly increased in 5 days after surgery. Both L-NAME and 7-NI ameliorated memory impairment induced by KA injection in passive avoidance response task. Only L-NAME improved KA-induced deficit in active avoidance response behavior. CONCLUSIONS: This study gives further evidence that NOS activation and excessive NO may mediate KA-induced excitotoxicity. Early and repetitive use of NOS inhibitors shows some protective effect on memory deficit induced by KA excitotoxicity.

Animals↗
PubMed2000

[Clinical analysis of glucose dysbolism in 162 cases with Cushing syndrome].

OBJECTIVE: To understand the characteristic of steroid diabetes by the analysis for clinical data of 162 cases with Cushing syndrome (CS) proved by pathological report. METHODS: Retrospective analysis for the data of CS about age of CS onset, duration of CS, body mass index (BMI), 24 hours urine free cortisol (24 h UFC), pathological report, fasting blood glucose (FBG) pre- and post-operation, family history of diabetes, treatment of glucose dysbolism (GD) pre- and post-operation. RESULTS: The onset age and duration of CS in GD group was obviously earlier and longer than normal glucose (NG) group. BMI and 24 h UFC were no difference between two groups. Besides adrenal adenocarcinoma, no difference was found in types of pathology. FBG of diabetes pre-operation was obviously lower than post-operation. After operation, most diabetes need not on drug treatment. Only one secondary diabetes has family history. CONCLUSIONS: Steroid diabetes easily occurs in patients who is senility and suffer longer course of CS. No relation to diabetic family history, concentric obesity, the level of UFC and benign types of pathology. Therapeutical emphasis of steroid diabetes is radical cure of CS.

Adolescent↗
PubMed2000

[Result of p53, ki-67 protein expression in cholangiocarcinoma with in situ hybridization and immunohistochemistry methods].

OBJECTIVE: To clarify the clinical significance of P53, ki-67, and the relationship between p53 gene expression and ki-67 labeling index. METHODS: In this study, 30 cases of human cholangiocarcinoma, paired with normal bile duct tissue adjacent to the tumor, were included. In situ hybridization (ISH) was used to detect the p53 gene expression. Immunohistochemistry (IHC) was applied to analyze p53 gene mutation and ki-67 labelling index. RESULTS: ki-67 and P53 positivity were detected in 96.7% (29/30) and 53.3% (16/30) of carcinoma specimens respectively by IHC, neither in peripheral normal tissue. p53 positivity was related to local lymph node metastasis. p53 positivity of cholangiocarcinoma in clinical stage III was significantly higher than that in clinical stage I, II. The expression of ki-67 protein was correlated with local lymph node metastasis and clinical stage. In lymph node metastasis group and clinical stage III group, ki-67 labeling index was significantly higher than that in non-lymph node metastasis group as well as in early stage group. We also found ki-67 labeling index of moderately or poorly differentiated cholangiocarcinoma was significantly higher than that of well differentiated carcinoma. Comparing survival time, the median survival time of patients whose bile duct tumors expressed no P53 protein or with lower ki-67 index was longer than that of patients whose tumors expressed P53 protein, or with higher ki-67 labeling index. CONCLUSIONS: The results indicate that p53 positivity may be correlated with tumor development, growing activity. They also indicate that ki-67 labeling index reflects the degree of tumor cell proliferation. This observation suggests that ki-67 labeling index may be a useful predictor of tumor prognosis.

Adult↗
PubMed2000

The effect of left ventricular diastolic dysfunction on the pathogenesis of angina decubitus.

OBJECTIVE: To investigate the effect of left ventricular diastolic dysfunction on the pathogenesis of angina decubitus (AD). METHODS: The study population consisted of three groups: 20 individuals without cardiovascular studied as group I. Group II included 20 patents with coronary artery disease and without AD. Thirty-one patients with AD and ejection fraction (EF) > 50% were studied as group III. Group II and III were matched for age, EF and extent of coronary artery disease. RESULTS: Left ventriculography (LVG) showed that left ventricular (LV) first 1/3 filling fraction (1/3FF) was significantly lower in group III than in group II and I (both P < 0.001), but LV late 1/3 FF was much higher in group III than in group II and I (P < 0.05, P < 0.01). Left ventricular end-diastolic pressure (LVEDP) was markedly increased before and after LVG in group II and III as compared with group I (both P < 0.05, both P < 0.001). The difference of LVEDP caused by left atrial contraction (left atrial contraction pressure difference, LACPD) before and after LVG was much higher in group III than in group I ( P < 0.01, P < 0.001). However, there we significant differences in LVEDP and in LACPD between before and after LVG only in group III (both P < 0.01). CONCLUSION: The patients with AD have LV diastolic dysfunction, which may be closely related to the pathogenesis of angina decubitus.

Adult↗
PubMed2000

[Vibrational and electronic spectra of a discrete and a tetramer containing [Mo3S7] core].

In this paper, the IR, Raman and UV-Vis spectra of a discrete cluster [Mo3S7(dtp)3I]1 and its tetramer [[Mo3S7(dtp)3]4I].[(HgI3)4].K]2(dtp = S2P(OC2H5)2-) were reported. The spectral characteristics of the compounds were discussed. According to the results of the studies on the structure and spectra, it was the weak intermolecular interaction and electrons transfer after tetramerization that led to the variation in the electronic structure of the compounds.

English Abstract↗
PubMed2000

[IR study on a series of tungsten clusters].

In this paper, the IR study on a series of tungsten clusters which contain a [W2S4]2+ or [W2MM'S4]4+ (M,M'=Cu,Ag) core is reported. According to the results of X-ray structural analysis and the IR spectra of the clusters, some characteristic IR absorptions of the clusters were assigned. The study of IR spectra of these clusters shows that the variation of structure can reflect on the IR spectra significantly.

Spectrophotometry, Infrared↗
PubMed2000

[Determination of palladium by ion exchange resin phase spectrophotometry].

A new method for the determination of palladium by ion exchange resin phase spectrophotometry has been established. It is based on the fixation of palladium as 1-(5-bromo-2-phridylazo)-2-naphthol-6-sulphonic acid (5-Br-PAN-S) compelled on a anion-exchange resin. The resin phase absorbances at 690 and 800 nm are measured directly and the linear range of 0-20 micrograms for palladium. The method has been applied to the determination of palladium in water samples and catalysts with satisfactory results.

Ion Exchange Resins↗
PubMed2000

[Determination of trace copper, zinc, iron, calcium and magnesium in lymph by flame atomic absorption spectrophotometry].

This paper reports the determination of trace Copper, Zinc, Iron, Calcium and Magnesium in lymph by flame atomic absorption spectrophotometry. The lymph samples were digested with HNO3-HClO4. The method is convenient and rapid. The rates of standard recovery of Copper, Zinc, Iron, Calcium and Magnesium were 99.2%, 103.0%, 102.0%, 104.0% and 98.5% respectively.

Calcium↗
PubMed1999

Expression cloning of protein targets for 3-phosphorylated phosphoinositides.

The phosphatidylinositol 3-kinase (PI 3'-K) family of lipid kinases play a critical role in cell proliferation, survival, vesicle trafficking, motility, cytoskeletal rearrangements, and oncogenesis. To identify downstream effectors of PI 3'-K, we developed a novel screen to isolate proteins that bind to the major products of PI 3'-K: phosphatidylinositol-3,4-bisphosphate (PtdIns-3,4-P(2)) and PtdIns-3,4,5-trisphosphate (PtdIns-3,4,5-P(3)). This screen uses synthetic biotinylated analogs of these lipids in conjunction with libraries of radiolabeled proteins that are produced by coupled in vitro transcription/translation reactions. The feasibility of the screen was initially demonstrated using avidin-coated beads prebound to biotinylated PtdIns-3,4-P(2) and PtdIns-3,4,5-P(3) to specifically isolate the pleckstrin homology domain of the serine/threonine kinase Akt. We then demonstrated the utility of this technique in isolating novel 3'-phosphorylated phosphatidylinositol (3'-PPI)-binding proteins through the preliminary screening of in vitro transcribed/translated cDNAs from a small pool expression library derived from mouse spleen. Three proteins were isolated that bound specifically to 3'PPIs. Two of these proteins have been previously characterized as PIP3BP/p42(IP4) and the PtdIns-3,4,5-P(3)-dependent serine/threonine kinase phosphoinositide-dependent kinase 1. The third protein is a novel protein that contains only a Src homology 2 domain and a pleckstrin homology domain; this protein has a higher specificity for both PtdIns-3,4,5-P(3) and PtdIns-3,4-P(2) than for PtdIns-4, 5-bisphosphate. Transcripts of this novel gene are present in every tissue analyzed but are most prominently expressed in spleen. We have renamed this new protein PHISH for 3'-phosphoinositide-interacting Src homology-containing protein. This report demonstrates the utility of this technique for isolating and characterizing 3'-PPI-binding proteins and has broad applicability for the isolation of binding domains for other lipid products.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Distinct specificities of inwardly rectifying K(+) channels for phosphoinositides.

Activation of several inwardly rectifying K(+) channels (Kir) requires the presence of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)). The constitutively active Kir2.1 (IRK1) channels interact with PtdIns(4,5)P(2) strongly, whereas the G-protein activated Kir3.1/3.4 channels (GIRK1/GIRK4), show only weak interactions with PtdIns(4,5)P(2). We investigated whether these inwardly rectifying K(+) channels displayed distinct specificities for different phosphoinositides. IRK1, but not GIRK1/GIRK4 channels, showed a marked specificity toward phosphates in the 4,5 head group positions. GIRK1/GIRK4 channels were activated with a similar efficacy by PtdIns(3,4)P(2), PtdIns(3,5)P(2), PtdIns(4,5)P(2), and PtdIns(3,4,5)P(3). In contrast, IRK1 channels were not activated by PtdIns(3,4)P(2) and only marginally by high concentrations of PtdIns(3,5)P(2). Similarly, high concentrations of PtdIns(3,4,5)P(3) were required to activate IRK1 channels. For either channel, PtdIns(4)P was much less effective than PtdIns(4,5)P(2), whereas PtdIns was inactive. In contrast to the dependence on the position of phosphates of the phospholipid head group, GIRK1/GIRK4, but not IRK1 channel activation, showed a remarkable dependence on the phospholipid acyl chains. GIRK1/GIRK4 channels were activated most effectively by the natural arachidonyl stearyl PtdIns(4,5)P(2) and much less by the synthetic dipalmitoyl analog, whereas IRK1 channels were activated equally by dipalmitoyl and arachidonyl stearyl PtdIns(4,5)P(2). Incorporation of PtdInsP(2) into the membrane is necessary for activation, as the short chain water soluble diC(4) PtdIns(4,5)P(2) did not activate either channel, whereas activation by diC(8) PtdIns(4, 5)P(2) required high concentrations.

Animals↗
PubMed1999

Human acyl-CoA:cholesterol acyltransferase-1 is a homotetrameric enzyme in intact cells and in vitro.

Acyl-CoA:cholesterol acyltransferase (ACAT) is a key enzyme in cellular cholesterol homeostasis and in atherosclerosis. ACAT-1 may function as an allosteric enzyme. We took a multifaceted approach to investigate the subunit composition of ACAT-1. When ACAT-1 with two different tags were co-expressed in the same Chinese hamster ovary cells, antibody specific to one tag caused co-immunoprecipitation of both types of ACAT-1 proteins. Radioimmunoprecipitations of cells expressing the untagged ACAT-1 or the 6-histidine-tagged ACAT-1 yielded a single radiolabeled band of predicted size on SDS-polyacrylamide gel electrophoresis. These results show that ACAT-1 exists as homo-oligomers in intact Chinese hamster ovary cells. We solubilized HisACAT-1 with the detergent deoxycholate or CHAPS (3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonic acid), performed gel filtration chromatography and sucrose density gradient centrifugations in H(2)O and D(2)O, and determined the Stokes radii and sedimentation coefficients of the HisACAT1-detergent complexes. The estimated molecular mass of HisACAT-1 is 263 kDa, which is 4 times that of the HisACAT-1 monomer (69 kDa). Finally, cross-linking experiments in intact cells and in vitro show that the increase in cross-linker concentrations causes an increase in size of the HisACAT-1-positive signals, forming material(s) 4 times the size of the monomer, supporting the conclusion that ACAT-1 is a homotetrameric enzyme.

Animals↗
PubMed1999

Evolution of shape complementarity and catalytic efficiency from a primordial antibody template.

The crystal structure of an efficient Diels-Alder antibody catalyst at 1.9 angstrom resolution reveals almost perfect shape complementarity with its transition state analog. Comparison with highly related progesterone and Diels-Alderase antibodies that arose from the same primordial germ line template shows the relatively subtle mutational steps that were able to evolve both structural complementarity and catalytic efficiency.

Antibodies, Catalytic↗
PubMed1999

An aerosol challenge mouse model for Moraxella catarrhalis.

A simple, reproducible, and non-invasive mouse pulmonary clearance model for Moraxella catarrhalis via aerosol challenge was established. All of eight tested strains could be inoculated into mice at more than 10(5) colony-forming units (CFU)/lung with a challenge concentration of 1x10(9)-6x10(9) CFU/ml in a nebulizer. The number of bacteria retained at 6 h postchallenge was more than 10(4) CFU/lung while at 24 h postchallenge, approximate 10(3) CFU/ml or less remained in the lungs. A maximum of 100 mice could be challenged per aerosol exposure. The number of bacteria inoculated in the lungs could be adjusted by the bacterial challenge concentration, the exposure time, and the negative pressure. Lung tissue sections revealed that bacteria were evenly distributed in the lungs. Passive immunization significantly enhanced pulmonary clearance of the homologous strain in this model. These data indicate that this model will be useful for evaluating M. catarrhalis vaccine candidates and studying roles of immunity against M. catarrhalis.

Aerosols↗