Biomedical subjects

L Y Chen

Publications and source records attributed to L Y Chen.

At least 37 records · Page 2Linked to original sources

PubMed2001

[Influence of human cytomegalovirus infection on the expressions of HOXB1, HOXB5, HOXB6, and HOXB9 genes in human embryo lung cells].

OBJECTIVE: To study the expressions of HOXB1, HOXB5, HOXB6, and HOXB9 genes in human embryo lung (HEL) cells and influence of human cytomegalovirus (HCMV) infection on the expressions of these genes. METHOD: The expressions of HOXB1, HOXB5, HOXB6, and HOXB9 genes were detected with semi-quantitative RT-PCR method. RESULTS: 1. HEL cells expressed HOXB5 and HOXB6 genes, but they did not express HOXB1 and HOXB9 genes. 2. After HCMV infection, HEL cell was induced to express HOXB9 gene, as the expression of HOXB6 gene was elevated. The expression of HOXB5 gene had no significant change. HOXB1 was still not expressed. 3. Treated with all-trans retinoic acid (ATRA), the expression of HOXB9 gene in HEL cells infected by HCMV was significantly increased. But during the advanced infect period, the expression of HOXB6 was significantly decreased. CONCLUSION: HCMV can induce abnormal expressions of HOXB6 and HOXB9 genes, which may play an important role in HCMV-induced abnormal embryogenesis.

Cells, Cultured↗

PubMed2001

[Study on molecular epidemiology of HCMV infection in mothers and their newborns in Changsha].

The detection of HCMV-IgG, IgM in plasma by ELISA and DNA in plasma and P(C) BMCs from mothers and their newborns by PCR was carried out. Positive HCMV-IgG, HCMV-IgM, P(C)BMCs HCMV DNA and plasma HCMV DNA were demonstrated in 119(95.2%), 7(5.6%), 27(21.6%) and 14(11.2%) in 125 mothers and 117(93.6%), 1(0.8%), 18(14.4%) and 7(5.6%) in their mewborns, respectively. There were significant differences among the positive rate of newborn's HCMV-IgM, plasma HCMV DNA and CBMCs HCMV DNA (P < 0.05), but the difference between HCMV-IgM and plasma HCMV DNA had no statistic significance (P > 0.05). This study suggests that HCMV-IgG and CBMCs HCMV PCR are preferable epidemiological index of HCMV infection of pregnant women and newborns respectively.

Adult↗

PubMed2001

Surgical correction of buried penis: a review of 60 cases.

BACKGROUND/PURPOSE: The authors reviewed 60 cases of buried penis, treated in a single institution with postoperative follow-up for at least 6 months. The review was aimed at providing information that might help to optimize the results in future surgical correction of this uncommon, but not rare, congenital disorder. METHODS: From January 1, 1989 to December 31, 1998, 62 boys with buried penis were treated with 1 of the following procedures: group 1A (n = 6), preputial unfurling alone; group 1B (n = 8), modified preputial unfurling; group 1C (n = 12), penoplasty devised by the first author with preservation of the preputial skin; and group 2 (n = 36), penoplasty with trimming of the inner preputial skin. Postoperative follow-up of more than 6 months after operation was achieved in 60 of 62 patients for a total of 25 patients in group 1 (A through C) and 35 patients in group 2. RESULTS: Recurrent buried penis developed in 8 of 60 patients (13%), and redundant penile skin with or without lymphedema occurred in 18 (30%). The complications occurred in 18 of 25 patients (72%) in group 1 (A through C) but in only 8 of 35 (23%) in group 2. The difference was significant (P =.001). Most of the complications were mild and acceptable. A second procedure was required in 5 of the 25 patients in group 1 but in none of group 2. The second procedures were required to correct recurrent buried penis in 1 and to resect excess redundant penile skin in 4. CONCLUSION: The superior results achieved in group 2 suggest that in addition to penoplasty with adequate fixation of the unfurling prepuce, resection of excess inner preputial skin is required to achieve an optimal outcome in children requiring surgical correction of buried penis.

Child↗

PubMed2001

Involvement of the XpsN protein in formation of the XpsL-xpsM complex in Xanthomonas campestris pv. campestris type II secretion apparatus.

The xps gene cluster is required for the second step of type II protein secretion in Xanthomonas campestris pv. campestris. Deletion of the entire gene cluster caused accumulation of secreted proteins in the periplasm. By analyzing protein abundance in the chromosomal mutant strains, we observed mutual dependence for normal steady-state levels between the XpsL and the XpsM proteins. The XpsL protein was undetectable in total lysate prepared from the xpsM mutant strain, and vice versa. Introduction of the wild-type xpsM gene carried on a plasmid into the xpsM mutant strain was sufficient for reappearance of the XpsL protein, and vice versa. Moreover, both XpsL and XpsM proteins were undetectable in the xpsN mutant strain. They were recovered either by reintroducing the wild-type xpsN gene or by introducing extra copies of wild-type xpsL or xpsM individually. Overproduction of wild-type XpsL and -M proteins simultaneously, but not separately, in the wild-type strain of X. campestris pv. campestris caused inhibition of secretion. Complementation of an xpsL or xpsM mutant strain with a plasmid-borne wild-type gene was inhibited by coexpression of XpsL and XpsM. The presence of the xpsN gene on the plasmid along with the xpsL and the xpsM genes caused more severe inhibition in both cases. Furthermore, complementation of the xpsN mutant strain was also inhibited. In both the wild-type strain and a strain with the xps gene cluster deleted (XC17433), carrying pCPP-LMN, which encodes all three proteins, each protein coprecipitated with the other two upon immunoprecipitation. Expression of pairwise combinations of the three proteins in XC17433 revealed that the XpsL-XpsM and XpsM-XpsN pairs still coprecipitated, whereas the XpsL-XpsN pair no longer coprecipitated.

Bacterial Proteins↗

PubMed2001

A common precursor for the three subunits of L-glutamate oxidase encoded by gox gene from Streptomyces platensis NTU3304.

A segment of DNA containing the L-glutamate oxidase (gox) gene from Streptomyces platensis NTU3304 was cloned. The entire nucleotide sequence of the protein-coding portion consisting of 2130 bp (710 codons, including AUG and UGA) of the cloned DNA fragment was determined. The gox gene contained only one open reading frame (ORF) which coded for a 78-kDa polypeptide, the precursor of active extracellular Gox. Mature Gox is composed of three subunits, designated as alpha, beta, and gamma, with molecular masses of 39, 19, and 16 kDa, respectively. Analyses of the N-terminal amino acid sequences of the subunits revealed that the order of subunits in the precursor polypeptide encoded by the ORF, from N-terminus to C-terminus, is alpha-gamma-beta. The presence of the flavin adenine dinucleotide (FAD)-binding motif place Gox as a member of the flavoenzyme family. Furthermore, a negative effect of glucose on the biosynthesis of Gox was observed when it was used as carbon source.

Amino Acid Oxidoreductases↗

PubMed2000

Benzylidene ketal derivatives as M2 muscarinic receptor antagonists.

Benzylidene ketal derivatives were investigated as selective M2 receptor antagonists for the treatment of Alzheimer's disease. Compound 10 was discovered to have subnanomolar M2 receptor affinity and 100-fold selectivity against other muscarinic receptors. Also, 10 demonstrated in vivo efficacy in rodent models of muscarinic activity and cognition.

Acetylcholine↗

PubMed2000

Structural requirements for the stability and microsomal transport activity of the human glucose 6-phosphate transporter.

Deficiencies in glucose 6-phosphate (G6P) transporter (G6PT), a 10-helical endoplasmic reticulum transmembrane protein of 429 amino acids, cause glycogen storage disease type 1b. To date, only three missense mutations in G6PT have been shown to abolish microsomal G6P transport activity. Here, we report the results of structure-function studies on human G6PT and demonstrate that 15 missense mutations and a codon deletion (delta F93) mutation abolish microsomal G6P uptake activity and that two splicing mutations cause exon skipping. While most missense mutants support the synthesis of G6PT protein similar to that of the wild-type transporter, immunoblot analysis shows that G20D, delta F93, and I278N mutations, located in helix 1, 2, and 6, respectively, destabilize the G6PT. Further, we demonstrate that G6PT mutants lacking an intact helix 10 are misfolded and undergo degradation within cells. Moreover, amino acids 415-417 in the cytoplasmic tail of the carboxyl-domain, extending from helix 10, also play a critical role in the correct folding of the transporter. However, the last 12 amino acids of the cytoplasmic tail play no essential role(s) in functional integrity of the G6PT. Our results, for the first time, elucidate the structural requirements for the stability and transport activity of the G6PT protein.

Amino Acid Sequence↗

PubMed2000

[Influence of human cytomegalovirus infection on the expression of HOX genes in human embryo lung cells].

The expressions of HOX genes in human embryo lung (HEL) cells were detected with semi-quantitative RT-PCR method. The results were that HEL cells expressed HOXB7 gene and its expression increased after human cytomegalovirus (HCMV) infection. The level of expression reached maximum at 48 h after HCMV infection. Treated with all-trans retinoic acid (ATRA), the expression of HOXB7 in HEL cells infected by HCMV was significantly increased. The results suggest that the abnormal expression of HOX genes induced by HCMV might possibly play a role in virus-induced abnormal embryogenesis.

Cells, Cultured↗

PubMed2000

Diphenylsulfone muscarinic antagonists: piperidine derivatives with high M2 selectivity and improved potency.

Piperidine analogues of our previously described piperazine muscarinic antagonists are described. Piperidine analogues show a distinct structure-activity relationship (SAR) that differs from comparable piperazines. Compounds with high selectivity and improved potency for the M2 receptor have been identified. The lead compound, 12b, increases acetylcholine release in vivo. Compounds of this class may be useful for the treatment of cognitive disorders such as Alzheimer's disease (AD).

Acetylcholine↗

PubMed2000

Retinoic acid-mediated G1 arrest is associated with induction of p27(Kip1) and inhibition of cyclin-dependent kinase 3 in human lung squamous carcinoma CH27 cells.

Retinoids are promising agents for the prevention and treatment of several human malignancies including lung cancer. In this study, the effect of retinoic acid (RA) on cell growth and the mechanism of growth modulation were examined in human lung squamous carcinoma CH27 cells. Here we report that RA mediated the dose- and time-dependent growth arrest in G1 phase, accompanied by the up-regulation of p27(Kip1) and the down-regulation of the cyclin-dependent kinase 3 (Cdk3) and p21(CIP1/Waf1) proteins. Furthermore, RA-induced growth arrest of CH27 cells was also associated with increased retinoic acid receptor beta (RARbeta) and reduced c-Myc expression. However, RA had no effect on the levels of cyclins A, D1, D3, E, or H, or on Cdk2, Cdk4, Cdk5, CDk6, Cdk7, p16(Ink4A), p15(Ink4B), p53, or pRb proteins in CH27 cells. Evaluation of the kinase activity of cyclin-Cdk complexes showed that RA increases p27(Kip1) expression in CH27 cells leading to markedly reduced cyclin A/Cdk2 kinase activity and slightly reduced cyclin E/Cdk2 kinase activity, with no effect on cyclin D/Cdk4 and cyclin D/Cdk6 activities. Moreover, coincident with the decrease in kinase activity was a drastic increase in cyclin A-bound p27(Kip1). These results suggest that increases in the levels of p27(Kip1) and its binding to cyclin A, as well as reduction of Cdk3 protein expression, are strong candidates for the cell cycle regulator that prevents the entry into the S phase in RA-treated CH27 cells, with prolongation of G1 phase and inhibition of DNA synthesis.

CDC2-CDC28 Kinases↗

PubMed2000

Cellular release of [18F]2-fluoro-2-deoxyglucose as a function of the glucose-6-phosphatase enzyme system.

[(18)F]-2-Fluoro-2-deoxyglucose (FDG) is a glucose analog currently utilized for positron emission tomography imaging studies in humans. FDG taken up by the liver is rapidly released. This property is attributed to elevated glucose-6-phosphatase (Glc-6-Pase) activity. To characterize this issue we studied the relationship between Glc-6-Pase activity and FDG release kinetics in a cell culture system. We overexpressed the Glc-6-Pase catalytic unit in a Glc-6-Pase-deficient mouse hepatocyte (Ho-15) and in A431 tumor cell lines. Glc-6-Pase enzyme activity and FDG release rates were determined in cells transfected with the Glc-6-Pase gene (Ho-15-D3 and A431-AC3), in mock-transfected cells of both cell lines, and in wild-type mouse hepatocytes (WT10) as control. Although the highest level of Glc-6-Pase activity was measured in A431-AC3, Ho-15-D3 cells showed much faster FDG release rates. The faster FDG release correlated with the level of glucose 6-phosphate transporter (Glc-6-PT) mRNA, which was found to be expressed at higher levels in Ho-15 compared with A431 cells. Overexpression of Glc-6-PT in A431-AC3 produced a dramatic increase in FDG release compared with control cells. This study gives the first direct evidence that activity of the Glc-6-Pase complex can be quantified in vivo by measuring FDG release. Adequate levels of Glc-6-Pase catalytic unit and Glc-6-PT are required for this function. FDG-positron emission tomography may be utilized to evaluate functional status of the Glc-6-Pase complex.

Animals↗

PubMed2000

Human monocyte adhesion and activation on crystalline polymers with different morphology and wettability in vitro.

This study evaluated the effects of crystalline polyamide (Nylon-66), poly(ethylene-co-vinyl alcohol) (PEVA), and poly(vinylidene fluoride) (PVDF) polymers with nonporous and porous morphologies on the ability of monocytes to adhere and subsequently activate to produce IL-1beta, IL-6, and tumor necrosis factor alpha. The results indicated monocyte adhesion and activation on a material might differ to a great extent, depending on the surface morphology and wettability. As the polymer wettability increases, the ability of monocytes to adhere increases but the ability to produce cytokines decreases. Similarly, these polymers, when prepared with porous surfaces, enhance monocyte adhesion but suppress monocyte release of cytokines. Therefore, the hydrophobic PVDF with a nonporous surface stimulates the most activity in adherent monocytes but shows the greatest inhibition of monocyte adhesion when compared with all of the other membranes. In contrast, the hydrophilic Nylon-66, which has a porous surface, is a relatively better substrate for this work. Therefore, monocyte behavior on a biomaterial may be influenced by a specific surface property. Based on this result, we propose that monocyte adhesion is regulated by a different mechanism than monocyte activation. Consequently, the generation of cytokines by monocytes is not proportional to the number of cells adherent to the surface.

Adult↗

PubMed2000

Thapsigargin-induced grp78 expression is mediated by the increase of cytosolic free calcium in 9L rat brain tumor cells.

Exposure of 9L rat brain tumor cells to 300 nM thapsigargin (TG), a sarcoendoplasmic Ca(2+)-ATPases inhibitor, leads to an immediate suppression of general protein synthesis followed by an enhanced synthesis of the 78-kDa glucose-regulated protein, GRP78. Synthesis of GRP78 increases significantly and continues to rise after 4 h of treatment, and this process coincides with the accumulation of grp78 mRNA. TG-induced grp78 expression can be suppressed by the cytosolic free calcium ([Ca(2+)](c)) chelator dibromo-1, 2-bis(aminophenoxy)ethane N,N,N',N'-tetraacetic acid (BAPTA) in a concentration-dependent manner. Induction of grp78 is completely abolished in the presence of 20 microM BAPTA under which the TG-induced increase of [Ca(2+)](c) is also completely prevented. By adding ethyleneglycol bis(beta-aminoethyl)ether-N,N,N',N' tetraacetic acid in the foregoing experiments, in a condition such that endoplasmic reticulum calcium ([Ca(2+)](ER)) is depleted and calcium influx from outside is prevented, TG-induced grp78 expression is also abolished. These data lead us to conclude that increase in [Ca(2+)](c), together with the depletion of [Ca(2+)](ER), are the major causes of TG-induced grp78 expression in 9L rat brain tumor cells. By using electrophoretic mobility shift assays (EMSA), we found that the nuclear extracts prepared from TG-treated cells exhibit an increase in binding activity toward the extended grp78 promoter as well as the individual cis-acting regulatory elements, CRE and CORE. Moreover, this increase in binding activity is also reduced by BAPTA. By competitory assays using the cis-acting regulatory elements as the competitors as well as the EMSA probes, we further show that all of the tested cis elements-CRE, CORE, and C1-are involved in the basal as well as in the TG-induced expression of grp78 and that the protein factor(s) that binds to the C1 region plays an important role in the formation and maintenance of the transcription complex.

Animals↗

PubMed2000

Genomic structure, expression, and chromosomal localization of the human glycine N-methyltransferase gene.

The glycine N-methyltransferase (GNMT) gene encodes a protein that not only acts as an enzyme to regulate the ratio of S-adenosylmethionine to S-adenosylhomocysteine, but also participates in the detoxification pathway in liver cells. Previously, we reported that the expression level of GNMT was diminished in human hepatocellular carcinoma. In this study, the human GNMT gene was cloned and characterized. It contains six exons and spans about 10 kb. Instead of a TATA box, it has a transcriptional initiator located 801 bp upstream from the translation start codon. The gene was localized to chromosome 6p12 using fluorescence in situ hybridization. Northern blot analysis of 16 tissues from different human organs showed that GNMT was expressed only in liver, pancreas, and prostate.

Adult↗

PubMed2000

fMet-Leu-Phe stimulates proinflammatory cytokine gene expression in human peripheral blood monocytes: the role of phosphatidylinositol 3-kinase.

The fMLP-stimulated release of proinflammatory cytokines such as IL-1 by human peripheral blood monocytes is an important component of the inflammatory process. The signaling mechanisms used by fMLP to stimulate the release of cytokines are still incompletely understood. We previously demonstrated that fMLP-stimulated NF-kappaB activation in PBMC and now we present evidence that the lipid products of phosphatidylinositol 3-kinase (PI 3-kinase) are required for fMLP-stimulated activation of NF-kappaB. Pretreatment with the PI 3-kinase inhibitors, wortmannin and LY294002, effectively blocked fMLP-induced IL-1beta gene expression as well as NF-kappaB activation. Transient transfection of THP1 cells with a dominant-negative mutant of the PI 3-kinase p85 subunit also abrogated fMLP-induced kappaB activity. These results suggest a potential role of fMLP in the transcription of proinflammatory cytokines and provide the first evidence that such regulation may occur through PI 3-kinase activity.

Cytokines↗

PubMed2000

Effects of tetrandrine on calcium transport, protein fluorescences and membrane fluidity of sarcoplasmic reticulum.

To understand whether the molecular mechanism of Tetrandrine (Tet)'s pharmacological effects is concerned with sarcoplasmic reticulum calcium transport so as to be involved in myocardial contractility, we observed the effects of Tet on calcium transport and membrane structure of rabbit skeletal muscle sarcoplasmic reticulum vesicles (SR) and rat cardiac sarcoplasmic reticulum vesicles (CSR). Calcium uptake was monitored with a dual-wavelength spectrophotometer. Protein conformation and fluorescence polarization were measured by fluospectrophotometric method and membrane lipids labelled with fluorescence probes for SR, respectively. 128 micromol l(-1) Tet reduced the initial rate of calcium uptake to 59% of control 6 min after reaction. Tet un-competitively inhibited SR Ca(2+), Mg(2+)-ATPase activity, causing the stoichiometric ratio of SR Ca(2+)/ATP to decrease to 1.43 from 2.0 of control. Inhibitory rates on SR Ca(2+),Mg(2+)-ATPase by Tet were reduced from 60% in the absence of phosphate to 50% in the presence of phosphate and reduced from 92% in 1 mmol l(-1) ATP to 60% in 5 mmol l(-1) ATP. Tet markedly reduced SR intrinsic protein fluorescence, while it slightly decreased the thiol(SH)-modified protein fluorescence of SR labelled with N-(3-pyrene)-maleimide. Tet slightly increased fluorescence polarization in the middle and deep layers of SR membrane lipids labelled with 7- or 12-(9-anthroyloxy) stearic acid (AS) probes, whereas it did not change that of SR labelled with 1, 6-diphenyl-1,3,5-hexatrine (DPH). These results revealed that prevention of SR calcium uptake by Tet was due to inhibition of the SR calcium pump Ca(2+),Mg(2+)-ATPase, changes in spatial conformation of the pumps protein molecules and a decrease in the extent of motion of membrane lipid molecules, thus altering the regulation of [Ca(2+)](i) and myocardial contractility.

Adenosine Triphosphate↗

PubMed2000

Possible effects of the Three Gorges dam on the transmission of Schistosoma japonicum on the Jiang Han plain, China.

The Three Gorges dam, under construction on the Yangtze River in China, might affect the transmission of Schistosoma japonicum on the Jiang Han plain, which is downstream of the dam. To study this possibility, the prevalence of schistosomiasis was investigated in relation to a range of malacological, hydrological and meteorological factors. The general water level in the Yangzte over a year had a marked effect on the distribution of the intermediate host (Oncomelania hupensis) and the prevalence of human schistosomiasis in that year. Disease prevalence showed significant correlations with the density of the snail hosts, the level of the water table, annual rainfall, yearly evaporation, and altitude. Once the dam is complete, the flow of water downstream will probably be maintained at a level between those currently occurring in flood and dry weather, and this may have implications for schistosome transmission. Systematic monitoring is necessary to investigate the impact of the environmental changes brought about by the dam on transmission.

Altitude↗

PubMed2000

Effect of stable fish oil on arterial thrombogenesis, platelet aggregation, and superoxide dismutase activity.

We examined the influence of dietary stable fish oil on aortic thrombosis, platelet aggregation, and superoxide dismutase (SOD) activity in a rat model. Twenty-nine Sprague-Dawley rats were fed regular chow supplemented with stable fish oil preparation (for 1 or 3 weeks), and 37 rats fed regular chow served as controls. The abdominal cavity was opened, and the abdominal aorta isolated. Whatman paper impregnated with 35% FeCl3 was wrapped around the surface of the aorta, and aortic flow was continuously recorded. In control rats, an occlusive platelet-fibrin-rich thrombus was formed in 21 +/- 3 min. Dietary fish oil in a time-dependent fashion delayed time to thrombus formation (24 +/- 2 min in rats fed fish oil for 1 week and 31 +/- 2 min in rats fed fish oil for 3 weeks), inhibited platelet aggregation (21 +/- 5% vs. 45 +/- 6%; p < 0.01) and increased SOD activity (p < 0.01). We conclude that dietary supplementation with stable fish oil delays formation of arterial thrombus, probably by reducing platelet aggregation and oxidative stress-associated arterial injury.

Animals↗