Biomedical subjects

Hua Xu

Publications and source records attributed to Hua Xu.

At least 55 records · Page 3Linked to original sources

PubMed2004

Facilitating cancer research using natural language processing of pathology reports.

Many ongoing clinical research projects, such as projects involving studies associated with cancer, involve manual capture of information in surgical pathology reports so that the information can be used to determine the eligibility of recruited patients for the study and to provide other information, such as cancer prognosis. Natural language processing (NLP) systems offer an alternative to automated coding, but pathology reports have certain features that are difficult for NLP systems. This paper describes how a preprocessor was integrated with an existing NLP system (MedLEE) in order to reduce modification to the NLP system and to improve performance. The work was done in conjunction with an ongoing clinical research project that assesses disparities and risks of developing breast cancer for minority women. An evaluation of the system was performed using manually coded data from the research project's database as a gold standard. The evaluation outcome showed that the extended NLP system had a sensitivity of 90.6% and a precision of 91.6%. Results indicated that this system performed satisfactorily for capturing information for the cancer research project.

Biomedical Research↗

PubMed2003

Large optical nonlinearities of new organophosphorus fullerene derivatives.

Optical nonlinearities of five new organophosphorus fullerene derivatives with similar structures were determined by the Z-scan method by use of a nanosecond-pulse laser at 532 nm. The experimental results demonstrate that the five derivatives have much larger excited-state absorption and nonlinear refraction than C60. The excited-state absorption cross sections are nearly two to three times that of C60. Using a five-level model to fit the experimental data, we obtained some parameters such as excited-state absorption and refraction cross sections. A simple analysis of correlations between molecular structure and nonlinear properties is given. Optical nonlinearities of the five new organophosphorus fullerene derivatives were compared with those of some other kinds of fullerene derivatives, and the results show that the nonlinearities of the new derivatives are the larger.

Journal Article↗

PubMed2003

A1 adenosine receptor knockout mice exhibit increased renal injury following ischemia and reperfusion.

Controversy exists regarding the effect of A1 adenosine receptor (AR) activation in the kidney during ischemia and reperfusion (I/R) injury. We sought to further characterize the role of A1 ARs in modulating renal function after I/R renal injury using both pharmacological and gene deletion approaches in mice. A1 AR knockout mice (A1KO) or their wild-type littermate controls (A1WT) were subjected to 30 min of renal ischemia. Some A1WT mice were subjected to 30 min of renal ischemia with or without pretreatment with 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) or 2-chrolo-cyclopentyladenosine (CCPA), selective A1 AR antagonist and agonist, respectively. Plasma creatinine and renal histology were compared 24 h after renal injury. A1KO mice exhibited significantly higher creatinines and worsened renal histology compared with A1WT controls following renal I/R injury. A1WT mice pretreated with the A1 AR antagonist or agonist demonstrated significantly worsened or improved renal function, respectively, after I/R injury. In addition, A1WT mice pretreated with DPCPX or CCPA showed significantly increased or reduced markers of renal inflammation, respectively (renal myeloperoxidase activity, renal tubular neutrophil infiltration, ICAM-1, TNF-alpha, and IL-1beta mRNA expression), while demonstrating no differences in indicators of apoptosis. In conclusion, we demonstrate that endogenous or exogenous preischemic activation of A1 ARs protects against renal I/R injury in vivo via mechanisms leading to decreased necrosis and inflammation.

Acute Kidney Injury↗

PubMed2003

Local anesthetics worsen renal function after ischemia-reperfusion injury in rats.

Local anesthetics are widely used during the perioperative period, even in patients with preexisting renal disease. However, local anesthetics have been shown to cause cell death in multiple cell lines, including human kidney proximal tubule cells. We questioned whether local anesthetics potentiate renal dysfunction after ischemia-reperfusion (I/R) injury in vivo. Rats were implanted with subcutaneous miniosmotic pumps that continuously delivered lidocaine (2 mg.kg-1.h-1), bupivacaine (0.4 mg.kg-1.h-1), tetracaine (1 mg.kg-1.h-1), or saline vehicle, and 6 h later the rats were subjected to 30 min of renal ischemia or to sham operation. Renal function was assessed by measurement of plasma creatinine at 24 and 48 h after renal I/R injury in the presence or absence of chronic infusions of local anesthetics and correlated to histological changes indicative of necrosis. The degree of renal apoptosis was assessed by three methods: 1) DNA fragmentation detected by terminal deoxynucleotidyl transferase biotin-dUTP nick-end labeling staining, 2) DNA laddering detected after agarose gel electrophoresis, and 3) morphological identification of apoptotic tubules at the corticomedullary junction. We also measured the expression of the proinflammatory markers ICAM-1 and TNF-alpha. Continuous local anesthetic infusion with renal I/R injury resulted in an increased magnitude and duration of renal dysfunction compared with the saline-infused I/R group. Additionally, both apoptotic and necrotic renal cell death as well as inflammatory changes were significantly potentiated in local anesthetic-treated rat kidneys. Local anesthetic infusion alone without I/R injury had no effect on renal function. We conclude that local anesthetics potentiated renal injury after I/R by increasing necrosis, apoptosis, and inflammation.

Anesthetics, Local↗

PubMed2003

Synthesis and characterization of faceted hexagonal aluminum nitride nanotubes.

The synthesis of the faceted single-crystalline h-AlN nanotubes with the length of a few micrometers and diameters from 30 to 80 nm is first reported. This provides an ideal substrate for the construction of GaN-based nanoheterostructures in future nanoelectronics. The experimental results suggest the further extensive experimental and theoretical studies on the promising nonlayered nanotubular structures.

Journal Article↗

PubMed2003

Oxidant preconditioning protects human proximal tubular cells against lethal oxidant injury via p38 MAPK and heme oxygenase-1.

Ischemic preconditioning protects the kidney from subsequent ischemic injury but the signal transduction pathways involved are unknown. Human proximal tubular (HK-2) cells were protected from injury with 2.5 mM H(2)O(2) by preconditioning with a single 15-min exposure to 500 microM H(2)O(2) followed by 16 h of recovery (oxidant preconditioning). To identify the signaling pathways involved in oxidant preconditioning, we utilized inhibitors of several signaling intermediates (MAPK/ERK kinase I, p38 mitogen-activated protein kinase (MAPK), protein kinase C and tyrosine kinase). A rapid but transient increase in p38 MAPK was observed following oxidant preconditioning and an inhibitor of p38 MAPK (SB203580) abolished the protection provided by oxidant preconditioning. Oxidant preconditioning was also associated with heat shock protein-27 phosphorylation (by p38 MAPK) and an increased synthesis of heme oxygenase-1 (HO-1). Stimulation or inhibition of HO-1 with hemin or Zn(II) protoporphyrin IX, respectively, mimicked or abolished oxidant preconditioning-mediated cytoprotection. Inhibitors of new protein synthesis (cycloheximide) and gene transcription (actinomycin D) also blocked the cytoprotection by oxidant preconditioning. We conclude that oxidant preconditioning protects HK-2 cells against more severe oxidant injury via activation of signaling pathways that include p38 MAPK and increased synthesis of HO-1.

Analysis of Variance↗

PubMed2003

Regulation of intestinal NaPi-IIb cotransporter gene expression by estrogen.

The current experiments were designed to study the effect of beta-estradiol on type IIb sodium-coupled phosphate (NaPi-IIb) cotransporter gene expression. Uptake studies with intestinal brush-border membrane vesicles (BBMV) showed that estrogen treatment increased sodium-dependent phosphate absorption by approximately 45% in rat intestine. Northern blot analysis indicated that NaPi-IIb mRNA expression was increased by approximately 50% after estrogen treatment. Western blot analysis also detected an increase in BBMV NaPi-IIb protein expression in estrogen-treated rats. In human intestinal Caco-2 cells, NaPi-IIb mRNA abundance was increased approximately 60% after estrogen treatment, and this increase could be abolished by inhibition of gene transcription. Transfection studies with human NaPi-IIb promoter reporter constructs showed that the promoter was responsive to estrogen treatment. These studies demonstrate for the first time that estrogen stimulates intestinal sodium-dependent phosphate absorption in female rats. This stimulation is associated with increased NaPi-IIb mRNA and protein expression. Thus the effect of estrogen on intestinal Pi absorption may be partially due to activation of NaPi-IIb gene transcription.

Animals↗

PubMed2003

Local anesthetics induce human renal cell apoptosis.

Renal cell apoptosis contributes significantly to the pathogenesis of acute renal failure. Local anesthetics induce apoptosis in neuronal and lymphocytic cell lines. We examined the effects of chronic (48 h) local anesthetic treatment (lidocaine, bupivacaine and tetracaine) on human proximal tubular (HK-2) cells. Apoptosis induction was assessed by detecting poly(ADP)-ribose polymerase fragmentation, caspase activation, terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) staining, DNA laddering and by cellular morphology. Cell death was quantified by measuring neutral red dye uptake and lactate dehydrogenase released into the cell culture medium. All 3 local anesthetics caused concentration-dependent cell death, induced HK-2 cell apoptosis and potentiated TNF-alpha induced apoptosis. Local anesthetics induced HK-2 cell apoptosis by activation of caspases 3, 6, 7, 8 and 9. ZVAD-fmk, a pan-caspase inhibitor, blocked the local anesthetic induced HK-2 cell apoptosis. Local anesthetics also inhibited the activities of anti-apoptotic kinases protein kinase B (Akt) and extracellular signal regulated mitrogen-activated protein kinase. Local anesthetic's pro-apoptotic effects are independent of sodium channel inhibition as tetrodotoxin, a selective voltage-gated sodium channel blocker, failed to mimic local anesthetic-mediated induction or potentiation of HK-2 cell apoptosis. We conclude that local anesthetics induce human renal cell apoptotic signaling by caspase activation and via inhibition of pro-survival signaling pathways.

Analysis of Variance↗

PubMed2003

Transcriptional regulation of the human NaPi-IIb cotransporter by EGF in Caco-2 cells involves c-myb.

The type IIb sodium-phosphate (NaP(i)-IIb) cotransporter mediates intestinal phosphate absorption. Previous work in our laboratory has shown that EGF inhibited NaP(i)-IIb cotransporter expression through transcriptional regulation. To understand this regulation, progressively shorter human NaP(i)-IIb promoter constructs were used to define the EGF response region, and gel mobility shift assays (GMSAs) were used to characterize DNA-protein interactions. Promoter analysis determined that the EGF response region was located between -784 and -729 base pair (bp) of the promoter. GMSAs and overexpression studies revealed an interaction between this promoter region and c-myb transcription factor. Inhibition of EGF receptor activation restored promoter function. Further studies suggested that MAPK, PKC, and/or PKA pathways are involved in this regulation. In conclusion, these studies suggest that EGF decreases human NaP(i)-IIb gene expression by modifying the c-myb protein such that it inhibits transcriptional activation. We further conclude that this downregulation of promoter function is mediated by EGF-activated PKC/PKA and MAPK pathways. This is the first study that demonstrates involvement of c-myb in the regulation of intestinal nutrient absorption.

Base Sequence↗

PubMed2003

[Preparation and identification of monoclonal antibodies against Penicillium marneffei].

OBJECTIVE: To prepare and identify monoclonal antibodies (mAbs) against Penicillium marneffei. METHODS: Recombinant mannoprotein1 (MP1) of Penicillium marneffei was used to immunize BALB/c mice, and anti-MP1 mAbs were obtained by means of hybridoma. Screening and identification of the mAbs were subsequently performed with indirect enzyme-linked immunosorbent assay and Western blotting, respectively. RESULTS: Four hybridomas producing antibodies against Penicillium marneffei were obtained, and the IgG isotypes of the 4 mAbs were identified as IgG1 with affinity constants (K) of 8.2x10(-9), 4.7x10(-9), 6.5x10(-9) and 2.7x10(-9), respectively. Western blotting demonstrated specific recognition of Aspergillus fumigatus MP1 by the obtained mAbs. CONCLUSION: The 4 hybridomas producing anti-MP1 mAbs with high specificity and affinity can be of significant value in the diagnosis of Penicilliosis marneffei infections.

Animals↗

PubMed2003

[Antibody response of patients with severe acute respiratory syndrome (SARS) to nucleocapsid antigen of SARS-associated coronavirus].

OBJECTIVE: To assess serum antibody responses of patients with severe acute respiratory syndrome (SARS) to nucleocapsid (N) antigen of SARS-associated coronavirus. METHODS: The serum levels of IgM and IgG antibodies to N antigen were measured in 200 healthy blood donors and 13 SARS patients at different time points of acute and convalescent phases using indirect enzyme-linked immunosorbent assay (ELISA) with N fusion proteins of SARS-associated coronaviruses. RESULTS: The IgM positive critical value of 0.233 and IgG of 0.239 were selected as the threshold value for positive results that equals the product of 2.1 and the mean IgM and IgG levels of 200 healthy blood donors. In 13 patients with SARS, the antibody responses to N antigen were not detectable in the first week after the onset of symptoms. The IgM and IgG seroprotection rates were 83.3% and 66.7% respectively in the second week, both reaching 100% at the third week. IgM seroprotection rates was 61.5% in the second month, and 38.5% at third month. The IgG peaked one month after the onset and remained at high levels in the following 2 months. CONCLUSION: The antibody responses suggest that N protein of SARS is immunodominant and plays an important role in viral pathogenesis. This ELISA-based test for detecting anti- N antigen may be of significant value for SARS diagnosis.

Antibodies, Viral↗

PubMed2003

Rapid and efficient preparation of monoclonal antibodies against SARS-associated coronavirus nucleocapsid protein by immunizing mice.

OBJECTIVE: To develop a rapid and efficient method for preparing monoclonal antibodies (mAb) against SARS-associated coronavirus (SARS-Cov) nucleocapsid (N) protein. METHODS: BALB/c mice were injected with the recombinant N protein of SARS-Cov into the foot-pads for the immunization, and the popliteal lymph nodes were isolated 15 d later for mAb-producing hybridomas, from which the mAbs against the N protein of SARS-Cov were screened. The identification of the mAb against the N protein of SARS-Cov was performed using indirect enzyme-linked immunosorbent assay (ELISA), indirect fluorescent-antibody assay (IFA), and Western immunoblotting. RESULTS: Four strains of hybridomas were obtained that produced the mAb specific to the N protein without detectable cross-reactivity with other pathogens. Of the 4 strains, 2 were identified as the immunoglobulin G1 (IgG1) isotype, 1 IgG2a, and the other IgG2b, with affinity constants (Ka) of 2 of the strains being 4.14 x 10(-9)M and 3.19 x 10(-9)M respectively. CONCLUSION: This is the first report on the preparation of mAb that is specific to the SARS-Cov, and the high-specificity and high-affinity mAb produced by the 4 strains of hybridomas provide a basis for further researches on the pathogenesis and early diagnosis of SARS.

Animals↗

PubMed2003

[Factors influencing CH4 emissions from a permanently flooded rice field during rice growing period].

Permanently flooded rice fields are the rice fields which emit the largest amount of CH4 in China. A 6-years (1995-2000) measurement carried out in a permanently flooded rice field in Chongqing, China showed that draining floodwater in winter and planting upland crops, either winter wheat or rape, instead of fallow under flooded conditions not only stopped CH4 emission during the winter season, but also mitigated CH4 emission during following rice growing period. CH4 emission could also be mitigated by ridge-cultivation. By using the results obtained from 1998-2000, statistical analysis indicated a significant relationship between the mean CH4 emission over the rice growing period and averaged soil moisture in winter season, which explained 56% of the variation of the CH4 emissions among the years and treatments. The averaged soil moisture (0-20 cm) in winter season and soil temperature (5 cm) over the rice growing period explained 78% of the variation. The significance of soil moisture in winter season in CH4 emission during the following rice growing period was further demonstrated by a lysimeter experiment. The relationships implied that the precipitation during non-rice growing period, which dominates soil moisture at a large spatial scale, and the soil temperature during the rice growing period would be the main factors controlling the annual variation of CH4 emissions from rice fields.

Methane↗

PubMed2003

[Antitumor effect of alcohol extract from Sesamum indicum flower on S180 and H22 experimental tumor].

OBJECTIVE: To investigate the antineoplasm effect of extract from Sesamum indicum L. flower. METHOD: Observing the effects of alcohol extract from Sesamum indicum flower on tumor growth in sarcoma 180 (S180) and Heps 22 (H22) tumorigenic mouse, and on weight of immune organs. RESULT: 6, 3, 1.5 g/kg extract showed inhibiting effect on tumor growth obviously, and had not distinct effect on weight of thymus and spleen in mice sarcoma 180 and Heps 22. CONCLUSION: The alcohol extract from Sesamum indicum flower showed obvious antitumor effect.

Animals↗

PubMed2003

Facilitating research in pathology using natural language processing.

Clinical research projects frequently rely on manual extraction of information from pathology reports, which is a costly and time-consuming process. This paper describes use of a natural language processing (NLP) system to automatically extract and structure information in textual pathology reports that is needed for clinical research.

Biomedical Research↗

PubMed2003

[Effects of different feeding methods on the iodine status of the infants during the weaning period].

OBJECTIVE: To investigate the iodine levels of urine from 1 month old breast-fed infants and the ones of milk and urine from the lactating women, and to observe the effects of different feeding methods (breast-feeding, mixed-feeding, bottle-feeding) on the iodine status of the infants during the weaning period in Beijing. METHODS: From March, 2001 to March, 2002, the iodine levels of urine from 97 breast-fed infants 1 month of age and the ones in milk and urine from lactating women were measured and compared. The infants followed up were divided into 3 groups (breast-fed, mixed and bottle-fed) until 6 months old. Their iodine levels of urine were measured and compared with the ones of 1 month of age. RESULTS: The median value of urine iodine from breast-fed 1 month old infants was 183 micro g/L, suggesting that the infants with breast-fed had good iodine nutritional status. The median value of urine iodine from lactating women was 122 micro g/L, significantly lower than the value of milk iodine, 201 micro g/L (P < 0.001). which suggests that the lactating women were iodine deficient but could provide infants iodine adequately through breast feeding. Compared with 1 month af age, the urine iodine levels of 6 months old infants with breast-feeding increased (P < 0.001), the ones with bottle-feeding decreased significantly (P < 0.001) and the mixed-feeding group did not change (P > 0.05). The differences among 3 groups were significant (P < 0.005), the urine iodine levels of infants of both breast-feeding and mixed-feeding groups were higher than the ones of bottle-feeding. The breast-feeding group was the highest one among three groups. CONCLUSION: The breast-fed infants were nourished with iodine, but the lactating women were iodine deficient. Accompanied the decrease of the amount of breast milk, the iodine levels of infants urine decreased during the weaning period, some bottle-feeding infants were iodine deficient.

Bottle Feeding↗

PubMed2002

Functional characterization of the human intestinal NaPi-IIb cotransporter in hamster fibroblasts and Xenopus oocytes.

The recently cloned NaPi-IIb cotransporter is an apical membrane protein that is involved in the absorption of phosphate in the intestine. To expedite functional and structural studies, the human intestinal NaPi-IIb cotransporter was stably expressed in hamster fibroblast (PS120) cells. The hNaPi-IIb cDNA stably transfected cells exhibited a 1.8-fold higher sodium-dependent phosphate uptake than vector DNA transfected cells, and had a K(m) for Pi of approximately 106 microM and a K(m) for Na(+) of approximately 34 mM. The hNaPi-IIb cotransporter was also expressed in Xenopus oocytes and it exhibited a K(m) for Pi of approximately 113 microM and a K(m) for Na(+) of approximately 65 mM. The hNaPi-IIb cotransporter expressed in both PS120 cells and oocytes was inhibited by high external pH. Furthermore, the phosphate uptake mediated by the hNaPi-IIb cotransporter was inhibited by 5 mM phosphonoformic acid (PFA), 1 mM arsenate and 100 nM phorbol myristate acetate (PMA). These results demonstrate that the human intestinal NaPi-IIb cotransporter is functional when expressed in hamster fibroblasts, and that this model system may be useful in the future to identify NaPi-IIb cotransporter-specific inhibitors.

Animals↗

PubMed2002

Controlled photochemical release of nitric oxide from O(2)-naphthylmethyl- and O(2)-naphthylallyl-substituted diazeniumdiolates.

The photochemistry of O2-naphthylmethyl- and O2-naphthylallyl-substituted diazeniumdiolates has been investigated. Electron-donating methoxy group substitution is shown to have a significant effect on the observed photochemistry, with the appropriate substitution pattern resulting in efficient diazeniumdiolate photorelease. Observed nitric oxide release rates from these photoprecursors are consistent with those expected for normal thermal dissociation of the diazeniumdiolate in aqueous solutions and show the same pH dependence.

Azo Compounds↗