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J Luo

Publications and source records attributed to J Luo.

At least 163 records · Page 9Linked to original sources
PubMed1999

In vivo activity of leflunomide: pharmacokinetic analyses and mechanism of immunosuppression.

BACKGROUND: Leflunomide is an experimental drug with demonstrated ability to prevent and reverse acute allograft and xenograft rejection. The two biochemical activities reported for the active metabolite of leflunomide, A77 1726, are inhibition of tyrosine phosphorylation and inhibition of dihydroorotate dehydrogenase, an enzyme necessary for de novo pyrimidine synthesis. These activities can be distinctly separated in vitro by the use of uridine, which reverses the anti-proliferative effects of A77 1726 caused by inhibition of de novo pyrimidine synthesis. We report the effect of uridine on the in vivo immunosuppressive activities of leflunomide. METHODS: We first quantified the serum levels of A77 1726, the active metabolite of leflunomide, after a single treatment of leflunomide (5, 15, and 35 mg/kg). Additionally, we quantified the levels of serum uridine and of nucleotide triphosphates in the liver, spleen, and lymph nodes of Lewis rats after the administration of a single dose of uridine (500 mg/kg; i.p.). Lewis rats heterotopically transplanted with brown Norway or Golden Syrian hamster hearts were treated for 50 or 75 days with leflunomide (5, 15, and 35 mg/kg/day; gavage) alone or in combination with uridine (500 mg/ kg/day; i.p.). Hematocrits were determined and the levels of alloreactive or xenoreactive immunoglobulin (Ig)M and IgG were determined by flow cytometric analysis. The allograft and xenografts, small bowel, liver, kidney, and spleen were subjected to pathological examination. RESULTS: A linear relationship was observed between the serum A77 1726 concentrations in Lewis rats and the dose of leflunomide administered. Peak A77 1726 concentrations were 20.9, 71.8 and 129.3 mg/l (77.5, 266.1 and 478.8 microM) for the 5, 15, and 35 mg/kg doses of leflunomide, respectively. The concentration of uridine in the serum of normal Lewis rats is 6.5 microM; after i.p. administration of 500 mg/kg uridine, the serum uridine concentrations peaked at 384.1 microM in 15-30 min. The rapid elimination of uridine was not reflected in the lymphoid compartments, and the pharmacokinetics of pyrimidine nucleotides in the spleen resembled that of A77 1726. This dose of uridine, when administered daily (500 mg/kg/day, i.p.), weakly antagonized the immunosuppressive activities of leflunomide (5, 15, and 35 mg/kg/day) in the allotransplantation model. In contrast, in the xenotransplantation model, the same concentration of uridine completely antagonized the immunosuppressive activities of low-dose leflunomide (15 mg/kg/day) and partially antagonized the immunosuppressive activities of high-dose leflunomide (35 mg/kg/day). Toxicities associated with high-dose leflunomide (35 mg/kg/day) were anemia, diarrhea, and pathological changes in the small bowel and liver. These toxicities were significantly reduced by uridine co-administration. CONCLUSION: These studies reveal that the blood levels of A77 1726 in Lewis rats satisfy in vitro requirements for both inhibition of de novo pyrimidine synthesis and protein tyrosine kinase activity. Our data also illustrate that the in vivo mechanism of immunosuppression by leflunomide is complex and is affected by at least the following four factors: type and vigor of the immune response, availability of uridine for salvage by proliferating lymphocytes, species being investigated, and concentration of serum A77 1726.

Aniline Compounds↗
PubMed1999

Suprachiasmatic nuclei monoamine metabolism of glucose tolerant versus intolerant hamsters.

A critical role for temporal organization of dopaminergic and serotonergic activities within the suprachiasmatic nuclei (SCN) in the regulation of peripheral glucose metabolism has been postulated. This study employed in vivo microdialysis to investigate the temporal extracellular profiles of dopamine and serotonin metabolites in the SCN of freely behaving naturally glucose tolerant and intolerant Syrian hamsters. Microdialysis samples from the right SCN of awake, glucose tolerant or intolerant hamsters held on 14 h daily photoperiods were collected every 2 h over a 24 h period and assayed via HPLC for the metabolites of dopamine: homovanillic acid (HVA) and serotonin (5-hydroxyindolacetic acid, 5-HIAA). Among glucose tolerant hamsters, daily rhythms of SCN HVA and 5-HIAA were observed with coincident plateaus throughout the nocturnal phase of the day (both p<0.01). Relative to glucose tolerant hamsters, glucose intolerant animals exhibited a loss in the daily rhythm of SCN HVA (p<0.0001) and 5-HIAA (p<0.02) due to marked reductions (70%) throughout the 24 h period in HVA levels and comparative decreases (35%) in nocturnal peak levels of 5-HIAA. These findings demonstrate that daily profiles of extracellular dopamine and serotonin activities in the SCN, known to influence glucose metabolism, differ between glucose tolerant and intolerant hamsters.

Analysis of Variance↗
PubMed1999

Noninflammatory expression of E-selectin is regulated by cell growth.

E-selectin, an endothelial-specific adhesion molecule best known for its role in leukocyte adhesion, is not detected in quiescent endothelial cells, but is induced by inflammatory stimuli. However, E-selectin is also expressed in proliferating endothelial cells under noninflammatory conditions in vivo and in vitro, suggesting that E-selectin is also regulated by growth signals. To investigate E-selectin expression in lipopolysaccharide-stimulated versus nonstimulated proliferating cells, we analyzed the distribution of E-selectin-positive human microvascular endothelial cells in G0/G1, S, and G2/M phases of the cell cycle under both conditions. Lipopolysaccharide treatment resulted in uniformly increased E-selectin expression in cells in G0/G1, S, and G2/M. In contrast, levels of E-selectin in nonstimulated proliferating cells showed a linear correlation with the percentage of cells in G2/M. E-selectin in proliferating endothelial cells was not reduced by addition of soluble tumor necrosis factor-alpha-receptor or soluble interleukin-1-receptor indicating that its expression was not due to endogenous production of either cytokine. In addition, E-selectin was increased in cells stimulated with basic fibroblast growth factor, a well-known mitogen for endothelial cells. E-selectin in proliferating endothelial cells is functional, as shown by E-selectin-dependent adhesion of the promyelocytic leukemia cell line HL-60 to subconfluent human microvascular endothelial cells. In summary, these studies indicate that E-selectin can be regulated by a non-inflammatory pathway that is related to the proliferative state of the endothelium.

Cell Adhesion↗
PubMed1999

A novel immunological model for the study of prostate cancer.

The Dunning R-3327 rat prostatic adenocarcinoma is a widely accepted model for in vivo experimental studies of prostate cancer. We have previously derived phenotypically distinct cell lines from a s.c. tumor resulting from the inoculation of the R-3327-5 subclone into Copenhagen rats. In this study, we report studies using a gelatin sponge model for the delivery of tumor cells and the retrieval of tumor-specific leukocytes responsive to different prostatic cell lines. S.c. preimplanted sponges were inoculated with tumor cells previously selected for differential properties of tumor formation and metastasis and examined for leukocyte content at time points of 1, 3, and 5 weeks after tumor cell inoculation. Cytospin and flow cytometric analyses revealed fewer tumor-associated leukocytes present in sponges inoculated with tumorigenic R-3327-5' and R-3327-5'B lines, with lesser sponge degradation, than in experiments with the nontumorigenic R-3327-5'A line, suggestive of a tumor cell-induced immunomodulatory mechanism. Morphological studies indicate an intermittent tumor growth pattern that gradually disappears in sponges inoculated with the nontumorigenic R-3327-5'A cells but a robust growth pattern in sponges inoculated with the tumorigenic cell lines. Cytokine analyses show the secretion of higher levels of active transforming growth factor-beta by the more invasive and metastatic lines. Total transforming growth factor-beta levels are higher in the epithelial, tumorigenic R-3327-5'B line. Additionally, the more tumorigenic lines secrete interleukin 10, a potent immunosuppressive molecule. In this report, we demonstrate the ability to retrieve viable leukocyte populations from a prostate tumor line bearing sponges, which offers an important model for further in vitro and in vivo manipulations and holds promise for testing adoptive immunotherapeutic strategies.

Adenocarcinoma↗
PubMed1999

Monocarboxylic-based phosphotyrosyl mimetics in the design of GRB2 SH2 domain inhibitors.

Three monocarboxylic-containing analogues, O-carboxymethyltyrosine (cmT, 5), 4-(carboxymethyl)phenylalanine (cmF, 6), and 4-(carboxydifluoromethyl)phenylalanine (F2cmF, 7) were utilized as phosphotyrosyl (pTyr) replacements in a high affinity B-bend mimicking platform, where they exhibited IC50 values of 2.5 microM, 65 microM and 28 microM, respectively, in a Grb2 SH2 domain Biacore binding assay. When a terminal N(alpha)-oxalyl axillary was utilized to enhance ligand interactions with a critical SH2 domain Arg67 residue (alphaA-helix), binding potencies increased from 4- to 10-fold, resulting in submicromolar affinity for cmF (IC50 = 0.6 microM) and low micromolar affinity for F2cmF (IC50 = 2 microM). Cell lysate binding studies also showed inhibition of cognate Grb2 binding to the p185erbB-2 phosphoprotein in the same rank order of potency as observed in the Biacore assay. These results indicate the potential value of cmF and F2cmF residues as pTyr mimetics for the study of Grb2 SH2 domains and suggest new strategies for improvements in inhibitor design.

Adaptor Proteins, Signal Transducing↗
PubMed1999

RARbeta mediates the response of Hoxd4 and Hoxb4 to exogenous retinoic acid.

One action of retinoids in development is the regulation of Hox gene expression. Hoxd4 and Hoxb4 expression in the embryonic hindbrain is anteriorized by retinoic acid (RA) treatment of mid-gestation mouse embryos. Here we demonstrate that retinoic acid receptor beta (Rarb) deficient mice present only a partial anteriorization of either Hoxd4 or Hoxb4 in response to RA treatment. Our results strongly suggest that RARbeta is a mediator of their RA-response, and reveal anteroposterior polarity within a single rhombomere (r). Additionally, we generated mice doubly mutated for Hoxd4 and Rarb in an attempt to identify common morphogenetic pathways between these two genes. We conclude that there are no synergistic interactions between Hoxd4 and Rarb in the specification of the cervical vertebrae.

Animals↗
PubMed1999

Anterolateral thigh flap: A review of 168 cases.

The anterolateral thigh flap based on the descending branch of the lateral circumflex femoral vessel is one of the musculocutaneous or septocutaneous flaps in the thigh. The descending branch of the lateral circumflex femoral vessel has either perforating branches or direct cutaneous branches from the intermuscular space to the anterolateral femoral skin. Since 1983, we have transferred 168 anterolateral thigh flaps for reconstruction of old burn scars, infected wounds, carcinoma excisions, for coverage of open bone fracture of the lower leg, and for congenital diseases. One hundred fifty-two cases were free flaps. The other 16 cases were pedicled flaps. The skin branches were divided into four types in our clinical series: musculocutaneous perforators (135/168 [80.4%]); intermuscular cutaneous perforators (16/168 [9.5%]); direct cutaneous branches (14/168 [8.3%]); and tiny cutaneous perforators (3/168 [1.8%]). The results were satisfactory. Only one case resulted in a failure due to tiny cutaneous branches.

Adolescent↗
PubMed1999

Study of temoporfin metabolism by HPLC and electrospray mass spectrometry.

The in vivo and in vitro metabolism of temoporfin (m-THPC), one of the most potent photosensitizers for the treatment of cancer by photodynamic therapy, has been studied in detail by HPLC with fluorescence and spectrophotometric detection and on-line HPLC-electrospray mass spectrometry. The results showed that temoporfin was not metabolized in vivo and was excreted unchanged via the biliary system into the faeces. No temoporfin or metabolites were detected in the urine. In vitro incubation of temoporfin with human and rat liver microsomal preparations in the presence of NADPH resulted in no metabolite production, even after enzyme induction with cytochrome P-450 isoenzyme inducers such as phenobarbitone, dexamethasone and 3-methylcholanthrene. No conjugation of temoporfin by phase II cytosolic enzymes was observed. It is concluded that the possible 'metabolites' previously observed were artifacts generated by photochemical oxidation of temoporfin to hydroxylated derivatives during the sample administration, collection, preparation and extraction procedures or were impurities already present in the original drug before administration for metabolic studies. These have been confirmed experimentally.

Animals↗
PubMed1999

Biochemical studies of the structure and function of the N-methyl-D-aspartate subtype of glutamate receptors.

The N-methyl-D-aspartate (NMDA) subtype of glutamate receptors plays a key role in synaptic transmission, synaptic plasticity, synaptogenesis, and excitotoxicity in the mammalian central nervous system. The NMDA receptor channel is formed from two gene products from two glutamate receptor subunit families, termed NR1 and NR2. Although the subunit composition of native NMDA receptors is incompletely understood, electrophysiological studies using recombinant receptors suggest that functional NMDA receptors consist of heteromers containing combinations of NR1, which is essential for channel activity, and NR2, which modulates the properties of the channels. The lack of agonists or antagonists selective for a given subunit of NMDA receptors has made it difficult to understand the subunit expression, subunit composition, and posttranslational modification mechanisms of native NMDA receptors. Therefore, most studies on NMDA receptors that examine regional expression and ontogeny have been focused at the level of the mRNAs encoding the different subunits using northern blotting, ribonuclease protection, and in situ hybridization techniques. However, the data from these studies do not provide clear information about the resultant subunit protein. To directly examine the protein product of the NMDA receptor subunit genes, the development of subunit-specific antibodies using peptides and fusion proteins has provided a good approach for localizing, quantifying, and characterizing the receptor subunits in tissues and transfected cell lines, and to study the subunit composition and the functional effects of posttranslational processing of the NMDA subunits, particularly the phosphorylation profiles of NMDA glutamate receptors.

Animals↗
PubMed1999

The effects of lower intensity anticoagulation therapy on coagulation system in patients with mechanical prosthetic valves.

To evaluate the effect of lower intensity anticoagulation therapy in patients with mechanical prosthetic valves, laboratory-based hematological assays including prothrombin time (PT), activity of factor X, antithrombin III (AT III), D-dimer, fibrinogen (Fg) and platel et al pha-granular membrane protein (GMP-140) were performed in 65 patients who had been on warfarin treatment for over one month. The patients were assigned to 3 groups on the basis of their International Normalized Ratios (INR), ranging from 2.00 to 2.50; 2.51 to 3.00; 3.01 to 4.50, respectively. The results showed that the D-dimer, Fg, GMP-140 levels were higher after mechanical valve replacement than those before operation, indicating the activation of coagulation and fibrinolysis system and the damage of platelets. Lower intensity anticoagulation therapy (INR 2.00 to 2.50) could effectively inhibit the activity of factor X and increase the level of AT III. There were no appreciable differences among D-dimer, Fg, GMP-140 and AT III in the 3 anticoagulation intensity groups. These results suggest that in patients with new generation mechanical prosthetic valves, target anticoagulation level (INR 2.00 to 2.50) may result in good protection from thrombo-embolism.

Adolescent↗
PubMed1999

Effect of masoprocol on carbohydrate and lipid metabolism in a rat model of Type II diabetes.

Extracts of the creosote bush (Larrea tridentata, family Zygophyllaceae) have long been used as a folk remedy for Type II (non-insulin-dependent) diabetes by native Americans in southwestern North America. In this study we have evaluated the metabolic effects of masoprocol, a pure compound isolated from the creosote bush, in a rat model of Type II diabetes. Animals were fed a 20% fat (by weight) diet for 2 weeks prior to intravenous injection with streptozotocin (STZ, 0.19 mmol/kg). Diabetic animals (glucose 16-33 mmol/l) were treated with vehicle, metformin (0.83 mmol/kg body weight) or masoprocol (0.83 mmol/kg body weight) twice a day for 4 days. Masoprocol treatment lowered glucose concentrations an average of 35% compared with vehicle (14.2+/-1.1 vs 21.7+/-1.0 mmol/l, p < 0.001), a reduction similar to metformin treatment (12.8+/-0.9 mmol/l), without any change in insulin concentration. Masoprocol treatment also lowered triglyceride concentrations 80% compared with vehicle (1.0+/-0.1 vs 4.8+/-0.3 mmol/l, p < 0.001), a reduction far greater than following metformin treatment (3.6+/-0.3 mmol/l). Non-esterified fatty acid and glycerol concentration were decreased by approximately 65% by masoprocol compared with vehicle, a reduction approximately twice as great as seen with metformin (p < 0.001). The effect of masoprocol on in vivo insulin-mediated glucose disposal was evaluated by infusing fat-fed/STZ rats with glucose (0.22 mmol kg x min(-1)) and insulin (30 pmol x kg x min(-1)) for 5 h. In response to the infusion, steady-state plasma glucose concentrations were reduced 30% in masoprocol-treated animals compared with vehicle controls (p < 0.05) with no change noted in rats treated with metformin. The effect of masoprocol treatment was also tested in primary adipocytes isolated from normal animals. Adipocytes treated with masoprocol (30 micromol/l) had higher basal and insulin-stimulated glucose clearance than did adipocytes treated with vehicle (p <0.05). These data show that masoprocol decreases both plasma glucose and triglyceride concentrations in fat-fed/STZ rats, presumably as a result of its ability to both increase glucose disposal and decrease lipolysis.

Adipocytes↗
PubMed1999

Antihyperglycemic sesquiterpenes from Psacalium decompositum.

Psacalium decompositum was investigated for antihyperglycemic compounds using diabetic ob/ob mice as a model for type 2 diabetes. In vivo bioassay-guided fractionation of an aqueous extract from the roots of P. decompositum led to the isolation of two new eremophilanolides, 3-hydroxycacalolide (1a) and epi-3-hydroxycacalolide (1b). A 1:1 mixture of 1a/1b exhibited antihyperglycemic activity when tested at 1.09 mmol/kg in ob/ob mice. The known furanoeremophilanes, cacalone (2a) and epicacalone (2b), were also isolated from the aqueous extract and were inactive. The known furanoeremophilane, cacalol (3), was isolated from a CH2Cl2 extract of P. decompositum roots and possessed antihyperglycemic activity. The relative stereochemistry in 1a and 1b was assigned 3R,5S and 3S,5S, respectively, based on ROESY data, 3J H-H values, and molecular mechanics calculations. Complete 13C and 1H NMR chemical shifts were assigned for 1a, 1b, 2a, 2b, and 3, and several revisions in 13C NMR assignments for 2a and 3 were made. Results from the conformational analysis of 1a, 1b, 2a, and 2b indicate that each compound exists in one major conformation in solution with H3-12 in a pseudoaxial position.

Animals↗
PubMed1999

Genetic diversity in crucian carp (Carassius auratus).

A survey of restriction fragment polymorphism in mitochondrial DNA of three subspecies of Carassius auratus throughout four provinces in China was undertaken using 17 restriction enzymes. Two carp, Cyprinus carpio rubbrofuscus and Cyprinus carpio carpio, were included as the outgroup. A total of 16 haplotypes was observed: 5 in tetraploids of C. auratus auratus; 8 in hexaploids of C. auratus auratus; and 2 in C. auratus gibelio and C. auratus cuvieri, respectively. The tetraploids and hexaploids share three common haplotypes as I, V, and VI. C. a. Cuvieri may have diverged first among the three subspecies. Interestingly, C. a. auratus and C. a. cuvieri did not form monophyletic clades, which indicated that the classification of Carassius auratus required further studies. The current hypothesis, that hexaploids originated from tetraploids by a polyploidy event, is less favorable, based on the distribution of haplotypes and the lower diversity in tetraploids than in hexaploids. Our data also indicate that divergence of hexaploids and tetraploids might be recent and mtDNA polymorphism existed before the divergence. Meanwhile, genetic isolation exists between the hexaploids and the tetraploids.

Animals↗
PubMed1999

Determination of interaction mechanism of sensorgrams by analysis of binding kinetics.

We monitored the interactions between pairs of molecules where the antigen adenylate kinase (AK) was immobilized on the surface of a chip and the antibody against AK, McAb3D3, was in solution. The association data that we obtained were not always accurately described by the expected pseudo-first-order reaction mechanism. A better description of the association data was achieved with a double-exponential function. Various models were applied to describe these observations: mass transport-controlled processes, inhomogeneous immobilized ligands, or inhomogeneous soluble analytes. Inhomogeneous immobilized ligands seemed to be the most likely explanation for the observed biphasic association kinetics. We simulated the kinetics of the SPR signal under the above-mentioned conditions. Plots of dR/dt versus R of the association phase showed characteristic differences between those nonlinearities resulting from mass transport limitation and those from inhomogeneous ligands. The plots of dR/dt versus R of McAb3D3 binding to immobilized AK show positive curvatures, indicating that the observed biphasic association kinetics is due to the inhomogeneity of the immobilized ligands. This is consistent with the results obtained from the comparison of various model fittings.

Adenylate Kinase↗
PubMed1999

Transforming growth factor beta1-regulated cell proliferation and expression of neural cell adhesion molecule in B104 neuroblastoma cells: differential effects of ethanol.

The expression and activity of factors influencing early neuronal development are altered by ethanol. Such factors include growth factors, for example, platelet-derived growth factor and basic fibroblast growth factor (for cell proliferation), and cell adhesion molecules (for neuronal migration). One agent, transforming growth factor beta1 (TGFbeta1), may affect both events. We tested the hypothesis that ethanol alters myriad TGFbeta1-mediated activities [i.e., cell proliferation and neural cell adhesion molecule (N-CAM) expression] using B104 neuroblastoma cells. TGFbeta1 inhibited the proliferation of B104 cells as evidenced by decreases in cell number and [3H]thymidine ([3H]dT) incorporation. TGFbeta1 induced sustained activation of extracellular signal-regulated kinases (ERKs), which are part of the family of mitogen-activated protein kinases (MAPKs). Treatment with PD98059 (a MAPK kinase blocker) abolished TGFbeta1-regulated inhibition of [3H]dT incorporation. TGFbeta1-mediated growth inhibition was potentiated by ethanol exposure. Ethanol also produced prolonged activation of ERK, an effect that was partially eliminated by treatment with PD98059. On the other hand, TGFbeta1 up-regulated N-CAM expression, and this up-regulation was not affected by treatment with PD98059. Ethanol inhibited the TGFbeta1-induced up-regulation of N-CAM expression in a concentration-dependent manner. Thus, TGFbeta1 affects ERK-dependent cell proliferation and ERK-independent N-CAM expression in B104 cells. Both activities are sensitive to ethanol and may underlie the ethanol-induced alterations in the proliferation and migration of CNS neurons.

Animals↗
PubMed1999

Distribution of two HIV-1-resistant polymorphisms (SDF1-3'A and CCR2-64I) in East Asian and world populations and its implication in AIDS epidemiology.

Chemokine receptor CCR2 and stromal-derived factor (SDF-1) are involved in HIV infection and AIDS symptom onset. Recent cohort studies showed that point mutations in these two genes, CCR2-64I and SDF1-3'A, can delay AIDS onset > or = 16 years after seroconversions. The protective effect of CCR2-64I is dominant, whereas that of SDF1-3'A is recessive. SDF1-3'A homozygotes also showed possible protection against HIV-1 infection. In this study, we surveyed the frequency distributions of the two alleles at both loci in world populations, with emphasis on those in east Asia. The CCR2-64I frequencies do not vary significantly in the different continents, having a range of 0.1-0.2 in most populations. A decreasing cline of the CCR2-64I frequency from north to south was observed in east Asia. In contrast, the distribution of SDF1-3'A in world populations varies substantially, and the highest frequency was observed in Oceanian populations. Moreover, an increasing cline of the SDF1-3'A frequency from north to south was observed in east Asia. The relative hazard values were computed to evaluate the risk of AIDS onset on the basis of two-locus genotypes in the east Asian and world populations.

Acquired Immunodeficiency Syndrome↗