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Biomedical subjects

Yan Xu

Publications and source records attributed to Yan Xu.

At least 145 records · Page 8Linked to original sources

Defective lipoxin-mediated anti-inflammatory activity in the cystic fibrosis airway.

In cystic fibrosis, dysregulated neutrophilic inflammation and chronic infection lead to progressive destruction of the airways. The underlying mechanisms have remained unclear. Lipoxins are anti-inflammatory lipid mediators that modulate neutrophilic inflammation. We report here that lipoxin concentrations in airway fluid were significantly suppressed in patients with cystic fibrosis compared to patients with other inflammatory lung conditions. We also show that administration of a metabolically stable lipoxin analog in a mouse model of the chronic airway inflammation and infection associated with cystic fibrosis suppressed neutrophilic inflammation, decreased pulmonary bacterial burden and attenuated disease severity. These findings suggest that there is a pathophysiologically important defect in lipoxin-mediated anti-inflammatory activity in the cystic fibrosis lung and that lipoxins have therapeutic potential in this lethal autosomal disease.

Cystic Fibrosis↗

An unsupervised approach to identify molecular phenotypic components influencing breast cancer features.

To discover a biological basis for clinical subgroupings within breast cancers, we applied principal components (PCs) analysis to cDNA microarray data from 36 breast cancers. We correlated the resulting PCs with clinical features. The 35 PCs discovered were ranked in order of their impact on gene expression patterns. Interestingly, PC 7 identified a unique subgroup consisting of estrogen receptor (ER); (+) African-American patients. This group exhibited global molecular phenotypes significantly different from both ER (-) African-American women and ER (+) or ER (-) Caucasian women (P < 0.001). Additional significant PCs included PC 4, correlating with lymph node metastasis (P = 0.04), and PC 10, with tumor stage (stage 2 versus stage 3; P = 0.007). These results provide a molecular phenotypic basis for the existence of a biologically unique subgroup comprising ER (+) breast cancers from African-American patients. Moreover, these findings illustrate the potential of PCs analysis to detect molecular phenotypic bases for relevant clinical or biological features of human tumors in general.

Adult↗

Role of Sonic hedgehog in patterning of tracheal-bronchial cartilage and the peripheral lung.

Sonic hedgehog (Shh) was conditionally deleted in respiratory epithelial cells of the embryonic lung in vivo. Deletion of Shh before embryonic day (E) 13.5 resulted in respiratory failure at birth. While lobulation was not perturbed, the lungs were hypoplastic, with reduced branching of peripheral lung tubules, evident from E13.5. Smooth muscle and endothelial cells were absent or reduced, the latter in relationship to the loss of peripheral lung parenchyma. Tracheal-bronchial ring abnormalities occurred when Shh was deleted between E8.5 and E12.5. Deletion of Shh later in gestation (after E13.5) caused mild abrogation of peripheral branching morphogenesis but did not disrupt tracheal-bronchial development. Defects in branching morphogenesis and vascularization seen in Shh null mutant (Shh(-/-)) mice were substantially corrected when SHH was ectopically expressed in the respiratory epithelium; however, peripheral expression of SHH failed to correct cartilage abnormalities in the trachea and bronchi, indicating a spatial requirement for SHH expression near sites of cartilage formation. Expression of SHH by the respiratory epithelium plays an important role in the patterning of tracheal-bronchial mesenchyme required for formation of cartilage rings in conducting airways. SHH regulates branching morphogenesis and influences differentiation of the peripheral lung mesenchyme required for formation of bronchial and vascular smooth muscle.

Animals↗

Expression of genes for collagen production and NF-kappaB gene activation of in vivo healing flexor tendons.

PURPOSE: Collagen production and reorientation are core events in the healing of tendons and are essential for gaining tensile strength. Intrasynovial flexor tendons are composed chiefly of type I collagen; however, type III collagen is the earliest to be laid down in the wounds. We investigated the expression of genes for type I collagen, type III collagen and its promoter, and nuclear transcription factor kappa B (NF-kappaB) in an in vivo tendon injury model in chickens. METHODS: Flexor digitorum profundus tendons of the long toes of 12 white leghorn chickens were transected partially and repaired with the modified Kessler method. The repaired tendon segments were harvested at 2, 4, and 8 weeks after surgery with 4 chickens used each time. The uninjured tendons from 4 other chickens were used as the controls. We determined the expression of the collagen and NF-kappaB genes in the tendons with reverse transcription and polymerase chain reaction and semiquantitative analysis of gene bands in gel electrophoresis. RESULTS: Expression of the type III collagen gene was enhanced significantly in the tendons at 2, 4, and 8 weeks after repair. Levels of expression of the type III collagen promoter gene were increased significantly in the healing tendons at 2 and 4 weeks. Increases in the expression of the type I collagen gene occurred later than those of the type III collagen and NF-kappaB genes and were significant in the tendons after 4 and 8 weeks. The NF-kappaB gene was activated in the tendons at all the healing periods. CONCLUSIONS: Expression of type III collagen and its promoter genes is enhanced remarkably during in vivo flexor tendon healing. The NF-kappaB gene is activated during the healing process. Expression of the type I collagen gene increases remarkably at later periods of in vivo tendon healing and is proportional to that of the NF-kappaB gene.

Animals↗

Biology of LPA in health and disease.

The functions of lysophosphatidic acid (LPA) can be broadly divided into two classes: (1) physiological and (2) pathological roles. The role of LPA in embryonic development can be seen as early as oocyte formation. It continues in postnatal homeostasis, through its ability to impart a level of protection from both stress and local injury, by regulating cellular proliferation, apoptosis, and the reorganization of cytoskeletal fibers. LPA may function as a double-edged sword. While it helps maintain homeostasis against stress and insult, it may also augment the development and spread of pathological processes, including cancers.

Breast Neoplasms↗

Expression of latent HAART-persistent HIV type 1 induced by novel cellular activating agents.

The novel antitumor-promoting phorbol ester, prostratin, was evaluated for its ability to induce the expression of latent, highly active antiretroviral therapy (HAART)-persistent human immunodeficiency virus type I (HIV-1) from specific subsets of patients' peripheral blood cells. This evaluation was performed relative to the use of other cellular activating agents, such as OKT3, a monoclonal antibody against the human T cell receptor, interleukin-2 (IL-2), phytohemagglutinin (PHA), p24 antigen (HIV-1-specific capsid protein), and a molecular relative of prostratin, 12-deoxyphorbol 13-phenylacetate (DPP). Prostratin performed as efficiently as the other cellular activators at inducing the expression of latent HIV-1 from cells of patients on virally suppressive HAART. Of interest was the induction of a novel species of latent virus from the cells of an individual after exposure to the HIV-1-specific capsid protein, p24, relative to virus expression induced by several other cell activators. This suggests that a variety of agents may be available for animal model studies of lentiviral latency and clinical use to broadly induce the expression of latent, HAART-persistent HIV-1 in vivo with the goal of potential HIV-1 reservoir depletion or eradication.

Amino Acid Sequence↗

DNA/MVA vaccine for HIV type 1: effects of codon-optimization and the expression of aggregates or virus-like particles on the immunogenicity of the DNA prime.

Recently, a vaccine consisting of DNA priming followed by boosting with modified vaccinia Ankara (MVA) has provided long-term protection of rhesus macaques against a virulent challenge with a chimera of simian and human immunodeficiency viruses. Here, we report studies on the development of the DNA component for a DNA/MVA HIV vaccine for humans. Specifically, we assess the ability of a codon-optimized Gag-expressing DNA and two noncodon-optimized Gag-Pol-Env-expressing DNAs to prime the MVA booster dose. The codon-optimized DNA expressed virus-like particles (VLPs), whereas one of the noncodon-optimized DNAs expressed VLPs and the other expressed aggregates of HIV proteins. The MVA boost expressed Gag-Pol and Env and produced VLPs. Immunogenicity studies in macaques used one intramuscular prime with 600 microg of DNA and two intramuscular boosts with 1 x 10(8) pfu of MVA at weeks 8 and 30. The codon-optimized and noncodon-optimized DNAs proved similar in their ability to prime anti-Gag T cell responses. The aggregate and VLP-expressing Gag-Pol-Env DNAs also showed no significant differences in their ability to prime anti-Env Ab responses. The second MVA booster dose did not increase the peak CD4 and CD8 T cell responses, but increased anti-Env Ab titers by 40- to 90-fold. MVA-only immunizations elicited 10-100 times lower frequencies of T cells and 2-4 lower titers of anti-Env Ab than the Gag-Pol-Env DNA/MVA immunizations. Based on the breadth of the T cell response and a trend toward higher titers of anti-Env Ab, we are moving forward with human trials of the noncodon-optimized VLP-expressing DNA.

AIDS Vaccines↗

Efficient generation of 2'-deoxyuridin-5-yl at 5'-(G/C)AA(X)U(X)U-3' (X = Br, I) sequences in duplex DNA under UV-irradiation.

A highly sequence-specific photoreaction of 5'-(G/C)AA(X)U(X)U-3' was found by using 450-base pair DNA fragments containing (X)U under UV-irradiation (X = Br, I). The molecular basis of this high photoreactivity was investigated in detail using synthetic octanucleotides. Based on the experimental data, the mechanism for the efficient photoreaction was proposed.

Base Sequence↗

Analysis of distamycin A binding to UV-damaged DNA.

We have found that distamycin A can bind to DNA duplexes containing the (6-4) photoproduct, one of the major UV lesions in DNA, in spite of the changes caused by photoproduct formation in the chemical structure of the base moiety and the local tertiary structure of the duplex. Distamycin binding was analyzed in detail using 14-mer duplexes. Curve fitting of the CD titration data and induced CD difference Spectra revealed that the binding stoichiometry changed from 1:1 to 2:1 with the photoproduct formation. Melting curves of the drug-DNA complexes also supported this stoichiometry.

Antiviral Agents↗

The recognition of Z-DNA by chiral helicene.

Enantiomeric helicenes of (P)-A and (M)-A were synthesized. The binding of the helicenes to B- and Z-DNA was studied quantitatively by CD, equilibrium dialysis, and fluorescence spectroscopy. Enantiomeric (P)-A not only bound selectively to Z-DNA, but also effectively converted the B-DNA conformation to Z-DNA. The enantio-selectivity of the helicenes offers a new route for the rational design of inhibitors of biological functions that may depend on Z-DNA.

Circular Dichroism↗

Tendon healing in vitro: activation of NIK, IKKalpha, IKKbeta, and NF- kappaB genes in signal pathway and proliferation of tenocytes.

Initiation of DNA transcription and proliferation of tendon cells are critical to tendon healing and require pivotal signals to the nucleus. Exploring intracellular signaling pathways pertinent to the healing process may reveal new approaches to accelerating the healing rate of the tendon. The authors investigated expression of NIK, IKKalpha, IKKbeta, and NF- kappaB genes in the signal pathway and tenocyte proliferation in an in vitro model in which cultured tenocytes were exposed to basic fibroblast growth factor (bFGF). Tenocytes were obtained from explant culture of rabbit intrasynovial tendons and were treated with bFGF at concentrations of 0, 2, or 10 ng/ml. Levels of expression of a series of genes for key factors along the signaling route--nuclear factor (NF)-kappaB-inducing kinase, inhibitor of kappa B kinase alpha and beta, and the NF-kappaB--were examined by quantitative analysis of products of reverse transcription and multiplex polymerase chain reactions. Proliferation of the cells was assessed with evaluation of growth curves and immunochemical labeling of the DNA of the cells. Expression levels of NIK, IKKalpha, IKKbeta, and NF-kappaB genes were significantly increased by bFGF at concentrations of 2 and 10 ng/ml. Western blot confirmed the increase of NF-kappaB in the tenocytes. The proliferation rate of the cells was significantly promoted by bFGF. Expression of these genes increased proportionately to the amounts of bFGF stimulating the cells and was correlated with increases in the proliferation rate. This study showed that expression of a series of genes along the NF-kappaB pathway was remarkably promoted by bFGF. The effects were proportionate to in vitro cell proliferation rate. Results of the study suggest that activation of a series of genes along the NF-kappaB pathway may play a pivotal role in initiating cell proliferation during the healing process of intrasynovial tendons. As activation of genes in signal transduction pathways is a new field in the biology of growth factor action with tremendous potential in promoting tissue repairs, manipulation of expression of a series of genes along the NF-kappaB pathway can be a new target of enhancing tendon healing through molecular mechanisms.

Animals↗

[The analysis of histopathology of conjunctivochalasis].

OBJECTIVE: To observe the histopathological change of conjunctivochalasis. METHODS: Conjunctival tissue was collected from 17 patients with conjunctivochalasis and 15 simple cataract patients. By HE/Verhoeff elastic fiber staining, the histopathological changes of conjunctival tissues in the patients were compared with those of simple cataract patients. RESULTS: The pathologic changes in conjunctivochalasis patients were characterized with hyperplasia of squamous epithelium with parakeratosis, pigmentation with different level in basal cell, hemorrhage, edema of stroma, infiltration of lymphocyte and plasmocyte. The elastic fiber layer was decreased. CONCLUSION: There was hyperplasia of conjunctival epithelium, decrease of elastic fiber and chronic inflammation in patients with conjunctivochalasis. The decrease of elastic fiber should be considered as major cause of the changes of conjunctiva.

Aged↗

[Effects of distractors on sustained attention in children with attention-deficit hyperactive disorder].

OBJECTIVE: Using an experimental design combining the sustained attention task (CPT, SART) and the flanker task, we investigated: 1) whether children with attention-deficit hyperactive disorder (ADHD) have deficits in their sustained attention; 2) whether distractors have different effects on response to targets at different sustained attention levels; 3) whether different subtypes of ADHD children show different patterns in sustained attention. METHODS: Subjects were recruited from elementary school (Grade 2 - 6). Twenty seven ADHD children (23 male, 4 female) and 29 normal controls (24 male, 5 female) were matched by IQ and age. The cognitive experiment measuring reaction times and error rates was conducted on a computer using DMDX software. ADHD and normal children's performance in sustained attention and the effect of distractors were analyzed, and the results of subtypes of ADHD were compared. RESULTS: ADHD children and normal children did not show significant differences in error rates in their response to dominant (non-attentional) item. However, distractors impaired ADHD children's response to targets. ADHD children also showed more errors than normal children in the sustained attention task, but compared with the non-distractor condition, distractors facilitated their response. CONCLUSIONS: ADHD children have deficits in their sustained attention, reflecting the deficits in brain development. More importantly, this study found that the effects of distractors in sustained attention can be dissociated according to the level of demand on sustained attention: distractors interfered with responses to targets when the demand on sustained attention was low, and they facilitated responses to targets when the demand on sustained attention was high. There were no significant differences between ADHD-inattentive type and ADHD-combined type in their deficits in sustained attention.

Attention↗

[Researches in forensic biomechanics].

Forensic biomechanics is the science of proof, which applies the biomechanical theory and technology to resolve problems related to mechanics in the process of expert witness. It belongs to the realm of a new subject combining biomechanics and forensics. Forensic biomechanics is a new branch of modern biomechanics and at the same time a new important branch of forensics, and it is one of the most potential research areas in forensics of injury. In this paper, the task of forensic biomechanics expert witness, the procedure of expert witness, and the forensic biomechanics research methods and cases are reviewed.

Biomechanical Phenomena↗

[Ocular pharmacokinetics of 0.5% pilocarpine with sodium hyaluronate in rabbits].

OBJECTIVE: To compare the pharmacokinetics of 0.5% pilocarpine containing sodium hyaluronate with 1% generic pilocarpine solution. METHODS: One hundred albino rabbits were divided into 20 groups, each consisting of 5 animals. Ten groups received 0.5% pilocarpine containing sodium hyaluronate and 10 groups received 1% generic pilocarpine solution as control. The aqueous humor was withdrawn at 5, 10, 20, 30, 40, 60, 90, 120, 150, and 180 min after instillation. The drug was extracted from aqueous humor with dichloromethane and was detected by reversed phase high performance liquid chromatography (HPLC). RESULTS: The average recovery rate of pilocarpine from aqueous humor was 98.2%. The minimum detectable concentration was 0.025 micro g/ml. The peak concentration and half-life of pilocarpine in aqueous humor were 4.46 micro g/ml at 10 min and 31.83 min, respectively, in the experimental group. Whereas, the peak concentration and half-life of pilocarpine in aqueous humor were 2.25 micro g/ml at 20 min and 22.98 min, respectively, in the control group. The peak concentration of pilocarpine in aqueous humor in the experimental group was 1.98 (P < 0.05) times higher than the control group. The area under curve of the drug concentration-time (AUC(0 - 180)) in the experimental group was 1.75 times higher than the control group. CONCLUSION: Pilocarpine (0.5%) containing sodium hyaluronate significantly increased the peak concentration of pilocarpine, shortened the time of reaching peak concentration and prolonged the half-life in aqueous humor. These results indicate that 0.5% pilocarpine with sodium hyaluronate significantly increases ocular bioavailability of pilocarpine.

Animals↗

Lysophospholipids are potential biomarkers of ovarian cancer.

OBJECTIVE: To determine whether lysophosphatidic acid (LPA) and other lysophospholipids (LPL) are useful markers for diagnosis and/or prognosis of ovarian cancer in a controlled setting. METHOD: Plasma samples were collected from ovarian cancer patients and healthy control women in Hillsborough and Pinellas counties, Florida, and processed at the University of South Florida H. Lee Moffitt Cancer Center and Research Institute (Moffitt). Case patients with epithelial ovarian cancer (n = 117) and healthy control subjects (n = 27) participated in the study. Blinded LPL analysis, including 23 individual LPL species, was performed at the Cleveland Clinic Foundation using an electrospray ionization mass spectrometry-based method. LPL levels were transmitted to Moffitt, where clinical data were reviewed and statistical analyses were performed. RESULTS: There were statistically significant differences between preoperative case samples (n = 45) and control samples (n = 27) in the mean levels of total LPA, total lysophosphatidylinositol (LPI), sphingosine-1-phosphate (S1P), and individual LPA species as well as the combination of several LPL species. The combination of 16:0-LPA and 20:4-LPA yielded the best discrimination between preoperative case samples and control samples, with 93.1% correct classification, 91.1% sensitivity, and 96.3% specificity. In 22 cases with both preoperative and postoperative samples, the postoperative levels of several LPL, including S1P, total LPA, and lysophosphatidylcholine (LPC) levels and some individual species of LPA and LPC, were significantly different from preoperative levels. CONCLUSION: LPA, LPI, LPC, and S1P appear useful as diagnostic and prognostic biomarkers of ovarian cancer.

Adolescent↗

Silver uptake by a marine diatom and its transfer to the coastal copepod Acartia spinicauda.

Silver (Ag) is an important metal contaminant in many coastal waters and often is accompanied by high nutrient concentrations in the effluent outfall. The biological uptake of Ag by the marine diatom Thalassiosira pseudonana at various levels of nitrate, ammonium, and phosphate was examined under different growth conditions of the cells. The biological uptake of Ag increased significantly with increasing concentrations of nitrate, ammonium, and phosphate, presumably because of the increase in algal growth rate or increasing sulfur-containing ligands available for Ag transport. The calculated Ag uptake rate constants increased by 3 to 16 times with increasing nitrate and ammonium concentration from 5.88 microM to 176 microM. The assimilation efficiency (AE) of Ag by the coastal copepod Acartia spinicauda was quantified under different ecological and chemical conditions of the diatom prey. The Ag AEs were in the range of 3 to 23%, and increased with decreasing diatom food concentrations or when the diatoms were grown at a lower nutrient level. Significant correlations were demonstrated between the AE and the distribution of Ag in the diatom's cytoplasm, the Ag concentration factor in the diatoms, Ag retention in the particles during the feeding period, and the Ag gut passage time in the copepods. Desorption within the copepod's gut appears to play a critical role in Ag assimilation and partially accounts for the variability of Ag AEs under different food and geochemical conditions. Our study highlights that several geochemical and physiological processes all significantly affect Ag trophic transfer in marine copepods. Given the dependence of Ag transfer on its concentration in ingested particles and food concentration, dietary uptake of Ag is probably variable in natural environments. The influence of eutrophication on Ag trophic transfer is dependent on the degree to which each kinetic parameter is affected by nutrient enrichments.

Animals↗

[Diagnosis and treatment of incidental prostate cancer following TUPVP (a report of 15 cases)].

OBJECTIVE: To investigate the diagnosis and treatment of incidental prostate cancer (IPC) following transurethral plasma kinetic vaporization prostatectomy (TUPVP). METHODS: Pathological examinations were conducted on 134 benign prostate hyperplasia specimens by means of series microtomy after TUPVP. RESULTS: Fifteen cases of IPC were detected from the total number of TUPVP specimens, with a pick-up rate of 11.2%. Dual testicle resection with endocrine therapy was performed in 4 cases of Stage A2 patients, and endocrine therapy alone was conducted in 9 cases of Stage A1 patients. Thirteen patients were followed up for 7 to 15 months and all lived without cancer (PSA 0.15 - 4.0 microg/L). CONCLUSION: TUPVP and series microtomy may be helpful to the diagnosis of IPC. Patients at Stage A1 need mere endocrine therapy, while those at Stage A2 warrant dual testicle resection.

Aged↗