Biomedical subjects

J Luo

Publications and source records attributed to J Luo.

At least 37 records · Page 2Linked to original sources

PubMed2001

Regulation of the CFTR channel by phosphorylation.

Cystic fibrosis transmembrane conductance regulator (CFTR) chloride channels are regulated tightly by protein kinases and phosphatases. The regulatory domain of CFTR has about 20 potential sites for phosphorylation by protein kinases A (PKA) and C (PKC). The reason for this large number of sites is not known, however their conservation from fish to humans implies that they play important roles in vivo. PKA is an important activator, and its stimulation of CFTR is enhanced by PKC via mechanisms which are not fully understood. The physiological stimuli of CFTR are not known for some epithelia, and it appears likely that other serine/threonine and even tyrosine kinases also regulate CFTR in particular tissues. Phosphatases that deactivate CFTR have yet to be identified definitively at the molecular level, however CFTR is regulated by a membrane-bound form of protein phosphatase-2C (PP2C) in several cell types. Patch-clamp studies of channel rundown, co-immunoprecipitation, chemical cross-linking studies, and pull-down assays all indicate that CFTR and PP2C are closely associated within a stable regulatory complex. Understanding the regulation of CFTR by PP2C is a priority due to its potential as a target for pharmacotherapies in the treatment of cystic fibrosis.

Cystic Fibrosis↗

PubMed2001

Human prostate cancer and benign prostatic hyperplasia: molecular dissection by gene expression profiling.

Critical aspects of the biology and molecular basis for prostate malignancy remain poorly understood. To reveal fundamental differences between benign and malignant growth of prostate cells, we performed gene expression profiling of primary human prostate cancer and benign prostatic hyperplasia (BPH) using cDNA microarrays consisting of 6500 human genes. Frozen prostate specimens were processed to facilitate extraction of RNA from regions of tissue enriched in either benign or malignant epithelial cell growth within a given specimen. Gene expression in each of the 16 prostate cancer and nine BPH specimens was compared with a common reference to generate normalized measures for each gene across all of the samples. Using an analysis of complete pairwise comparisons of expression profiles among all of the samples, we observed clearly discernable patterns of overall gene expression that differentiated prostate cancer from BPH. Further analysis of the data identified 210 genes with statistically significant differences in expression between prostate cancer and BPH. These genes include many not recognized previously as differentially expressed in prostate cancer and BPH, including hepsin, which codes for a transmembrane serine protease. This study reveals for the first time that significant and widespread differences in gene expression patterns exist between benign and malignant growth of the prostate gland. Gene expression analysis of prostate tissues should help to disclose the molecular mechanisms underlying prostate malignant growth and identify molecular markers for diagnostic, prognostic, and therapeutic use.

Gene Expression Profiling↗

PubMed2001

Pancreatic cancer cell-derived vascular endothelial growth factor is biologically active in vitro and enhances tumorigenicity in vivo.

Vascular endothelial growth factor (VEGF) is a potent angiogenic stimulator that acts by binding to high-affinity transmembrane receptors. Although both VEGF and its receptors are overexpressed in human pancreatic ductal adenocarcinoma (PDAC), this malignancy is not generally considered to be highly vascular. It is not known, therefore, whether the abundance of VEGF in PDAC is biologically relevant. To address this issue, we measured the angiogenic effects of pancreatic cancer cell-derived VEGF in an in vitro endothelial cell proliferation assay and characterized the consequences of suppressing VEGF expression on pancreatic tumor growth in an athymic nude mouse model. We found that human pancreatic cancer cell lines secrete large quantities of biologically active VEGF into conditioned medium (CM). Stable transfection of an anti-sense VEGF(189) (AS-VEGF(189)) expression construct into PANC-1 pancreatic cancer cells resulted in decreased VEGF expression and secretion, a decreased capacity of the resultant CM to enhance endothelial cell proliferation and a significant attenuation of tumor cell proliferation in vitro. Furthermore, when injected into athymic nude mice, AS-VEGF(189)-expressing cells exhibited an 80% decrease in tumor growth compared with control cells. These results support the hypothesis that VEGF promotes pancreatic cancer growth in vivo and suggest that anti-VEGF therapy may be useful in the treatment of this disease.

Animals↗

PubMed2001

Non-small cell lung cancer cyclooxygenase-2-dependent invasion is mediated by CD44.

Elevated tumor cyclooxygenase (COX-2) expression is associated with increased angiogenesis, tumor invasion, and suppression of host immunity. We have previously shown that genetic inhibition of tumor COX-2 expression reverses the immunosuppression induced by non-small cell lung cancer (NSCLC). To assess the impact of COX-2 expression in lung cancer invasiveness, NSCLC cell lines were transduced with a retroviral vector expressing the human COX-2 cDNA in the sense (COX-2-S) and antisense (COX-2-AS) orientations. COX-2-S clones expressed significantly more COX-2 protein, produced 10-fold more prostaglandin E(2), and demonstrated an enhanced invasive capacity compared with control vector-transduced or parental cells. CD44, the cell surface receptor for hyaluronate, was overexpressed in COX-2-S cells, and specific blockade of CD44 significantly decreased tumor cell invasion. In contrast, COX-2-AS clones had a very limited capacity for invasion and showed diminished expression of CD44. These findings suggest that a COX-2-mediated, CD44-dependent pathway is operative in NSCLC invasion. Because tumor COX-2 expression appears to have a multifaceted role in conferring the malignant phenotype, COX-2 may be an important target for gene or pharmacologic therapy in NSCLC.

Adenocarcinoma↗

PubMed2001

[Retrospective analysis of argon laser for treating retinal periphlebitis].

OBJECTIVES: This article was to investigate the curative effect of argon laser photocoagulation for retinal periphlebitis treatment, and then to discuss the stage of the treatment. METHODS: According to the condition of vitreous hemorrhage and the range of retinal neovascularization, 31 cases (34 eyes) were divided into the light group and the heavy group, and the therapeutic effective rate, the condition of visual acuity and vitreous hemorrhage were compared. RESULTS: The therapeutic effective rate was 64.71%, there was significant difference in effective rate and prognosis of visual acuity between two groups (P < 0.01). After laser treatment, the morbidity of vitreous hemorrhage in heavy group decreased from 100% to 18.70%. CONCLUSION: Argon laser photocoagulation is an effective method for treating retinal periphlebitis and early treatment is recommended.

Adolescent↗

PubMed2001

Go!Poly: A gene-oriented polymorphism database.

Human genome polymorphisms play a key role in defining the molecular basis of phenotypic differences between individuals in aspects such as disease susceptibility and drug responses. The database requirements for supporting the study of human genetic variation have been well recognized. In order to meet these needs, several generalized databases have been built. However, it is still hard for users to find gene-related variation data from these huge and sophisticated databases. In its role as a gene-oriented directory of polymorphism data, Go!Poly (Gene Oriented Polymorphism Database; http://61.139.84.5/gopoly/) utilizes two new highly curated and non-redundant resources, LocusLink (http://www.ncbi.nlm.nih.gov/LocusLink/) and RefSeq (http://www.ncbi.nlm.nih.gov/LocusLink/refseq.html), as the standard for identifying and positioning nucleotide variations. As a generalized polymorphism database, Go!Poly extracts human gene-linked sequence variations of all common types (SNP, insertion-deletion, simple tandem repeat, and complex nucleotides variations) from various public resources including scientific journals and internet resources, such as HGBASE (http://hgbase.cgr.ki.se) and dbSNP (http://www.ncbi.nlm.nih.gov/SNP/). The polymorphism data are then categorized into different gene loci, and the reference sequences given by LocusLink are used as positioning references. Through close integration with LocusLink, Go!Poly also provides facilitated connections among sequence data, gene name, and related biological information. This feature also makes Go!Poly easy to search and navigate. Future automated annotations and internal consistency checking may also benefit from this. Extensive efforts are being taken to make the polymorphism information generated by the Chinese scientific community available from this resource.

China↗

PubMed2001

Expression patterns of vitamin D receptor in human prostate.

UV exposure and serum levels of vitamin D have been linked in several studies with prostate cancer risk. At the cellular level, the principal action of vitamin D is mediated though vitamin D receptors (VDR). Since prostate cancer is a disease strongly associated with age, we examined the presence of VDR in normal prostate from donors of various ages to determine if the VDR expression pattern changed with age. We also compared the VDR expression in the peripheral and central zones of the prostate to determine if the expression pattern varied by location. Immunohistochemical studies were performed on paraffin-embedded tissue from cases selected by the following age decades; 10-19, 20-29, 30-39, 40-49, 50-59, and 60-69. Both the central and peripheral zones were examined for VDR expression. The intensity of VDR expression in prostate was compared with expression in different types of human tissues. Mean VDR expression was lowest in the 10-19 years of age group. The intensity of the nuclear VDR was higher though the fifth decade, and then declined in cases of ages 60-70. When multiple sections of the same donor prostate were compared, VDR expression was greater in the peripheral zone compared to the central zone.

Adolescent↗

PubMed2001

Identification of estrogen-responsive genes in chick liver.

Identification of targets of estrogen is an important step in understanding the mechanisms of estrogen action. A two-step strategy was developed to identify estrogen-responsive genes (ERGs) in chick liver. Initially, differential-display, reverse transcription polymerase chain reaction (DDRT-PCR) was introduced to isolate ERGs. Isolated ERGs were then analyzed using Northern blot hybridization. A number of differentially expressed cDNA fragments were isolated following estrogen exposure. Four cDNA fragments that displayed dramatic change after estrogen administration were identified as liver adenylosuccinate lyase (ADL), phenobarbital-inducible cytochrome P-450 (CYP450), ovoinhibitor, and glutathione-dependent prostaglandin D2 synthase (PGDS). Time sequence analysis showed that estrogen-induced alteration occurred as early as 0.5 h and peaked between 1 and 4 h after estrogen exposure. Nuclear runoff assay indicated that estrogen significantly increased the transcription rate of these genes. To determine whether the observed alteration was due to the direct effect of estrogen, protein synthesis was inhibited by cycloheximide (CHX) during stimulation by estradiol, Estrogen-mediated upregulation of PGDS was completely abolished by a concurrent treatment with CHX, suggesting that its activation requires the participation of some newly synthesized factor(s). In contrast, CHX did not affect the expression of other genes, indicating the alteration is a direct response to estrogen. In conclusion, ADL, CYP450, ovoinhibitor, and PGDS represent the novel targets of estrogen, which regulates the transcriptional activity of these genes.

Adenosine Monophosphate↗

PubMed2001

Elevated potassium intake inhibits neointimal proliferation in the swine coronary artery.

BACKGROUND: Previously, we reported that elevated extracellular potassium concentration in vitro inhibited proliferation and migration of vascular smooth muscle cells, formation of free radical compounds by macrophages, and reduced platelet sensitivity to agonists. More recently, we described a reduction in neointimal proliferation after balloon angioplasty injury in the carotid arteries of rats associated with an elevation of dietary potassium intake during a 4-week experiment. In the present study we conducted a similar investigation in the swine coronary artery balloon angioplasty model. PROCEDURES: Two groups of seven castrated male swine were studied; for 28 days the normal potassium group consumed a diet containing 0.25% potassium and the high potassium group ate diet containing 2.0% potassium. After 14 days on the diet, balloon angioplasty was performed. After an additional 14 days on the same diets the hearts were removed, and normal and lesioned sections of the artery were analyzed histologically. RESULTS: The neointimal area was markedly less in the high potassium group than in the normal potassium group, 0.33+/-0.04 mm2 v 0.74+/-0.10 mm2 (P < .004). Neointimal area-to-total wall area ratio in the normal potassium group averaged 0.199+/-0.018, significantly greater than the ratio computed for the elevated potassium group, 0.120+/-0.015 (P < .006). CONCLUSION: These results support the hypothesis that a high level of dietary potassium intake inhibits neointimal proliferation after balloon angioplasty in the swine coronary artery.

Aldosterone↗

PubMed2001

Influence of stent edge angle on endothelialization in an in vitro model.

PURPOSE: To investigate the influence of topographic features in the path of migrating endothelial cells, specifically the effect of edge angle of intravascular metallic material on endothelialization. MATERIALS AND METHODS: Flat 1-cm x 1-cm 316-L pieces of stainless steel were placed on confluent monolayers of human aortic endothelial cells. The thickness of each metal piece was ground to achieve an edge angle of 35 degrees, 70 degrees, 90 degrees, or 140 degrees (n = 6 each) in relation to the endothelial surface. Migration distance and density of endothelial cell coverage on the metal pieces were measured in groups of six each under static conditions at 4, 7, and 11 days and flow conditions (16 dynes/cm(2)) at 4 days. RESULTS: Endothelial cell migration distance along the surface of the pieces with edge angles of 35 degrees was significantly greater than that with those with larger angles (P < .05) under static and flow conditions. The migration distances on the 35 degrees piece were 87.5%, 47.3%, 57.1%, and 66.1% greater than those on the 90 degrees piece at the upstream, downstream, right, and left edges, respectively. There were no significant differences in cell density among different angle groups under flow or static conditions. CONCLUSION: The edge angle of intravascular metallic material has an influence on the rate of endothelialization. A smaller edge angle facilitates endothelialization over metallic material when compared to a larger angle. These results demonstrate the importance of metallic stent profile on endothelialization rate.

Cell Movement↗

PubMed2001

Modulation of expression of ribosomal protein L7a (rpL7a) by ethanol in human breast cancer cells.

Epidemiological studies indicate that there is a positive correlation between alcohol consumption and the risk of breast cancer. Experimental results demonstrate that ethanol is a tumor promoter and chronic ethanol exposure enhances metastasis and growth of breast cancer. The present study used an in vitro model to investigate the molecular mechanism(s) underlying tumor promoting effects of ethanol. With differential display reverse transcription polymerase chain reaction, we demonstrated that human ribosomal large subunit protein L7a (rpL7a) was an ethanol-responsive factor in T47D breast cancer cells. The results of northern blot hybridization revealed that the effect of ethanol on L7a expression was duration- and concentration-dependent. Initial exposure resulted in a 2-fold increase in rpL7a level, whereas a longer exposure period produced a down-regulation. Ethanol had little effect on the stability of rpL7a mRNA; however, the transcription rate of rpL7a was significantly increased by ethanol. Ethanol-induced up-regulation of rpL7a was not a simple stress response, because other stress inducers, such as heat shock, did not affect the expression of rpL7a. Furthermore, breast cancer cells expressed higher level of rpL7a than normal mammary epithelial cells. Ribosomal proteins are known to play an important role in translational regulation, and they have been implicated in the control of cellular transformation, tumor growth, aggressiveness and metastasis. Specially, rpL7a activates the trk oncogene by contributing an amino-terminal-activating sequence to the receptor kinase domain of trk. Thus, ethanol-induced alteration of rpL7a expression may mediate the promoting effects of ethanol on breast cancer development.

Alcohol Drinking↗

PubMed2001

Family-based transmission disequilibrium test (TDT) and case-control association studies reveal surfactant protein A (SP-A) susceptibility alleles for respiratory distress syndrome (RDS) and possible race differences.

A key cause of respiratory distress syndrome (RDS) in the prematurely born infant is deficiency of pulmonary surfactant, a lipoprotein complex. Both low levels of surfactant protein A (SP-A) and SP-A alleles have been associated with RDS. Using the candidate gene approach, we performed family-based linkage studies to discern linkage of SP-A to RDS and identify SP-A susceptibility or protective alleles. Moreover, we performed case-control studies of whites and blacks to detect association between RDS and SP-A alleles. Transmission disequilibrium test (TDT) analysis revealed that the frequency of transmission (from parent to the offspring with RDS) of alleles 6A(2) and 1A(0) and of 1A(0)/6A(2) haplotype in RDS was increased, whereas transmission of alleles 1A(5) and 6A(4) and of haplotype 1A(5)/6A(4) was decreased. Extended TDT analysis further strengthened the observations made. The case-control studies showed that in whites or blacks with RDS the frequencies of specific genotypes, 1A(0) and 6A(2) or 1A(0), were increased, respectively, but the frequency of specific 6A(3) genotypes was increased in certain white subgroups and decreased in blacks. Regression analysis revealed gestational age (GA) and 6A(3) genotypes are significant factors in blacks with RDS. In whites with RDS, GA and antenatal steroids are important factors. The data together indicate linkage between SP-A and RDS; certain SP-A alleles/haplotypes are susceptibility (1A(0), 6A(2), 1A(0)/6A(2)) or protective (1A(5), 6A(4), 1A(5)/6A(4)) factors for RDS. Some differences between blacks and whites with regard to SP-A alleles may exist.

Alleles↗

PubMed2001

Surfactant protein (SP) B associations and interactions with SP-A in white and black subjects with respiratory distress syndrome.

BACKGROUND: The etiology of respiratory distress syndrome (RDS) is multifactorial and/or multigenic. Surfactant protein A (SP-A) and/or SP-B genetic variants have been identified as risk or protection factors for RDS. METHODS: We genotyped subjects with and without RDS for the SP-B intron 4 size variants (invariant (inv), deletion (del), insertion (ins) and for four (-18 (A/C), 1013 (A/C), 1580 (C/T), 9306 (A/G)) SP-B single nucleotide polymorphisms (SNP), to study case-control associations in black and white subjects. We also determined whether specific SP-B variants interact with RDS susceptibility or protective SP-A variants to enhance or reduce risk for RDS. RESULTS: Based on odds ratio: (1) the SP-B intron 4 del variant in white subjects is more of an RDS risk factor for males and for subjects of 28 weeks <gestational age (GA)<33 weeks; (2) the SP-B intron 4 ins variant in black subjects is more of an RDS risk factor in females; (3) in white subjects, SP-A1 (6A(2)/6A(2)) or SP-A2 (1A(0)/1A(0) or 1A(0)/*) genotypes in subjects of certain GA and with a specific SP-B genotype (9306 (A/G) or del/*) are associated with an enhanced risk for RDS; (4) in black subjects, SP-A1 (6A3/6A(3) or 6A(3)/*) genotypes in subjects of 31 weeks < or = GA < or = 35 weeks and with the SP-B (1580 (T/T)) genotype are associated with a reduced risk for RDS. CONCLUSIONS: The SP-B polymorphisms are important determinants for RDS. These may identify differences between black and white subjects, as well as, between males and females regarding the risk for RDS. Furthermore, SP-A susceptibility or protective alleles, in specific SP-B background, are associated, based on OR, with an increased or reduced risk for RDS.

Alleles↗

PubMed2001

Differential effects of ethanol on the expression of cyclo-oxygenase in cultured cortical astrocytes and neurons.

The developing central nervous system is a primary target of ethanol toxicity. The teratogenic effect of ethanol may result from its action on prostaglandins. Prostaglandins are generated through the release of arachidonic acid (AA) by the action of cytosolic phospholipase A(2) (cPLA(2)) on membrane-bound phospholipids and the catalytic conversion of AA to prostaglandin E(2) (PGE(2)) by cyclo-oxygenase (COX). COX is expressed in two isoforms, constitutive COX1 and inducible COX2. Cultured astrocytes and neurons from immature cerebral cortex were used as in vitro models to investigate the effect of ethanol on PGE(2) synthesis. In both cell types, neither the activity nor the expression of cPLA(2) was affected by ethanol. PGE(2) was synthesized by astrocytes and neurons. Ethanol (200-400 mg/dL for 24 h) significantly increased PGE(2) production in both cell types and the ethanol-induced increase in PGE(2) accumulation in astrocytes was significantly greater than in neurons. These increases resulted from the effects of ethanol on COX. Overall COX activity was up-regulated by ethanol in astrocytes and neurons, and indomethacin, a nonselective blocker for COX, eliminated the ethanol-induced increases of COX activity in both cell types. Increased COX activity in astrocytes resulted from an increase in COX2 expression. NS-398, a selective COX2 blocker, completely inhibited ethanol-induced alterations in COX activity. In neurons, however, ethanol had a direct effect on COX activity in the absence of a change in COX expression. NS-398 only partially blocked ethanol-induced increases in neuronal COX activity. Thus, astrocytes are a primary target of ethanol and ethanol-induced increases in glial PGE(2) synthesis are mediated by COX, principally COX2. Ethanol toxicity may be mediated through PGE(2) in immature cortical cells.

Animals↗

PubMed2001

Gas characteristics before and after biofiltration treating odorous emissions from animal rendering processes.

Studies of odour-control biofilters at two animal rendering plants were conducted. Biofilter influent and effluent gases were characterized using a gas chromatograph-mass spectrometer (GC-MS) and a GC fitted with an odour sniffing port. Overall odour-removal performance of the biofilters was evaluated using forced-choice dynamic-dilution olfactometers. GC-MS analysis revealed that the biofilter influent gases at each plant contained about 300 compounds. About 20% of these compounds were identified, and included hydrocarbons, ketones, heterocyclics, aldehydes, aromatics, carobxylic acids, esters, sulphur compounds, nitriles, an amine and an amide. About 20 identified compounds were present in both biofilter influent gases. The influent gas at Plant 1 contained more straight chain hydrocarbons, while the influent gas at Plant 2 contained more sulphur compounds and esters. Sensory evaluation of the gas samples using the GC-odour port technique indicated that about 45 compounds in the biofilter influent gases were odorous at Plant 1, and about 30 were odorous at Plant 2. A variety of odour characters was observed in the two biofilter influent gases. The biofilters reduced the concentration of most of the odorous compounds to levels that were not detectable by the GC-odour port analysis. The rendering process gases had odour concentrations of between 59,000 and 1,000,000 OU m(-1). The biofilters reduced the odour concentration by 82-99% and also reduced the "offensiveness" of the odour. Uneven gas distribution affected biofilter odour-removal performance.

Abattoirs↗

PubMed2001

Production of cloned goats from enucleated oocytes injected with cumulus cell nuclei or fused with cumulus cells.

This study was designed to produce cloned goats from cumulus cells. Cloning donor nuclei were from cumulus cells either freshly isolated or cultured in vitro. Enucleated oocytes were either injected with cumulus cell nuclei without piezo-driven manipulator (injection method) or fused with cumulus cells (fusion method). The survival rate of cloned embryos, obtained by injection, was higher than that derived from fusion (62.7 and 45.9%, respectively). Two cloned goats were derived by fusion with in vitro cultured cumulus cells without starvation, but died shortly after natural birth, from respiratory difficulties. Their birth weights (2.23 kg and 2.03 kg) were within the normal range (2.0-2.7 kg) and postmortem analysis revealed no morphological abnormalities. The third cloned goat, derived by injection of nuclei from freshly isolated cumulus cells, weighed 3.3 kg at birth, and was 37% overweight compared with the average weight of the same species. This goat is healthy and well as this paper is being prepared. Nested PCR-RFLP analysis confirmed that all the cloned goats were derived from the donor cells.

Animals↗

PubMed2001

Antibody-antigen interactions measured by surface plasmon resonance: global fitting of numerical integration algorithms.

The interactions between adenylate kinase (AK) and a monoclonal antibody against AK (McAb3D3) were examined by means of optical biosensor technology, and the sensograms were fitted to four models using numerical integration algorithms. The interaction of a solution of McAb3D3 with immobilized AK follows a double exponential function and the data fitted well to an inhomogeneous ligand model. The interaction of a solution AK with immobilized McAb3D3 follows a single exponential function and the data fitted well to a pseudo-first order reaction model. The true association constants of AK binding to McAb3D3 in solution were obtained from competition BIAcore measurements. The difference in results obtained with solid-phase BIAcore and competition BIAcore may be due to rebinding of the dissociated analyte to the immobilized surface. The results obtained with BIAcore are compared to those obtained by ELISA methods. We suggest that the best method for analysis of BIAcore data is direct, global fitting of sensorgrams to numerical integration algorithms corresponding to the different possible models for binding.

Adenylate Kinase↗

PubMed2001

Structural analysis of free and enzyme-bound amaranth alpha-amylase inhibitor: classification within the knottin fold superfamily and analysis of its functional flexibility.

The three-dimensional structure of the amaranth alpha-amylase inhibitor (AAI) adopts a knottin fold of abcabc topology. Upon binding to alpha-amylase, it adopts a more compact conformation characterized by an increased number of intramolecular hydrogen bonds, a decreased volume and in addition a trans to cis isomerization of Pro20. A systematic analysis of the 3-D structural databanks revealed that similar proteins and domains share with AAI the characteristic presence of proline residues, many of which are in a cis backbone conformation. As these proteins fulfil a variety of functional roles and are expressed in very different organisms, we conclude that the structure of the knottin fold, including the propensity of the cis bond, are the result of convergent evolution.

Algorithms↗