Biomedical subjects

Jia Li

Publications and source records attributed to Jia Li.

At least 55 records · Page 3Linked to original sources

PubMed2006

A computationally efficient approach to the estimation of two- and three-dimensional hidden Markov models.

Statistical modeling methods are becoming indispensable in today's large-scale image analysis. In this paper, we explore a computationally efficient parameter estimation algorithm for two-dimensional (2-D) and three-dimensional (3-D) hidden Markov models (HMMs) and show applications to satellite image segmentation. The proposed parameter estimation algorithm is compared with the first proposed algorithm for 2-D HMMs based on variable state Viterbi. We also propose a 3-D HMM for volume image modeling and apply it to volume image segmentation using a large number of synthetic images with ground truth. Experiments have demonstrated the computational efficiency of the proposed parameter estimation technique for 2-D HMMs and a potential of 3-D HMM as a stochastic modeling tool for volume images.

Algorithms↗

PubMed2006

Construction of a small peptide library related to inhibitor OM99-2 and its structure-activity relationship to beta-secretase.

AIM: To develop probes for detecting the binding specificity between beta-secretase and substrate, and provide reliable biological activity data for further researching encircling substrate-based inhibitors. METHODS: To prepare the inhibitors, the hydroxyethylene (HE) segment including P1 and P1'was synthesized after multi-step reactions; the combination of all segments was then completed through solid phase synthesis. Recombinant human beta-secretase ectodomain (amino acid residues 1-460) was expressed as a secreted protein with a C-terminal His tag in insect cells using baculovirus infection, and all compounds were evaluated in this beta-secretase enzyme assay. In order to understand the interaction in detail, the theoretical methods, namely molecular dynamics (MD) simulation and molecular mechanics-generalized-born surface area (MM-GBSA) analysis, were performed on the complex of beta-secretase and OM99-2 to obtain the geometrical and energetical information. RESULTS: We designed and constructed a positional scanning combinatorial library including 16 compounds; all members of the library were synthesized based on HE dipeptide isostere. Structure-activity relationship studies at the P4-P1 and P1' -P4'positions led to the discoveries of P and P'sides binding specificity and potent inhibitors 14, 18, and 22. The binding free energy on the whole system and every residue were compared to the biological assay result. CONCLUSION: The removal of P4' yielded inhibitor 22 (A3 *B2) with high potency; further truncation of P3'gave inhibitor 18 (A3 *B1) with equal activity, implying that the right side of the inhibitors play a less important role and could be easily simplified, while change on the P side may cause substantial results.

Amyloid Precursor Protein Secretases↗

PubMed2006

Isolation and characterization of monoclonal antibodies which neutralize human metapneumovirus in vitro and in vivo.

Human metapneumovirus (hMPV) is a recently described member of the Paramyxoviridae family/Pneumovirinae subfamily and shares many common features with respiratory syncytial virus (RSV), another member of the same subfamily. hMPV causes respiratory tract illnesses that, similar to human RSV, occur predominantly during the winter months and have symptoms that range from mild to severe cough, bronchiolitis, and pneumonia. Like RSV, the hMPV virus can be subdivided into two genetic subgroups, A and B. With RSV, a single monoclonal antibody directed at the fusion (F) protein can prevent severe lower respiratory tract RSV infection. Because of the high level of sequence conservation of the F protein across all the hMPV subgroups, this protein is likely to be the preferred antigenic target for the generation of cross-subgroup neutralizing antibodies. Here we describe the generation of a panel of neutralizing monoclonal antibodies that bind to the hMPV F protein. A subset of these antibodies has the ability to neutralize prototypic strains of both the A and B hMPV subgroups in vitro. Two of these antibodies exhibited high-affinity binding to the F protein and were shown to protect hamsters against infection with hMPV. The data suggest that a monoclonal antibody could be used prophylactically to prevent lower respiratory tract disease caused by hMPV.

Antibodies, Monoclonal↗

PubMed2006

[Insulin prevents injury and enhances survival of rat hepatocytes via its anti-inflammatory effects].

AIM: To investigate whether insulin exerts protective effects against hepatocytes injury indirectly induced by LPS and if so, the mechanism involved. METHODS: Kupffer cells and hepatocytes were isolated from male Sprague-Dawley rats by pronasecollagenase perfusion and cultured. Kupffer cells were stimulated by lipopolysaccharide (LPS) or LPS+insulin for 4 h, the supernatant of different groups were collected to detect TNF-alpha and IL-10 by ELISA and to stimulate the primary cultured rat hepatocytes with or without anti-TNF-alpha antibody. After the hepatocytes were stimulated for 12 h, cell survival rate and injury indexes were detected. RESULTS: (1) The supernatant of LPS-activated Kupffer cells caused significant hepatocytes injury. Treatment with insulin produced a potent protective effect as evidenced by decreased ALT and AST levels (P<0.01, n=8) and improved hepatocytes survival rate (P<0.01, n=8). (2) Compared with the LPS group, insulin significantly decreased TNF-alpha secretion (P<0.01, n=8) and increased IL-10 secretion (P<0.05, n=8) from Kupffer cell stimulated by LPS. (3) Incubating hepatocytes with anti-TNF-alpha antibody attenuated hepatocytes injury induced by the supernatant of LPS-activated Kupffer cells. But treatment with anti-TNF-alpha antibody and insulin did not exert additive effect compared with treatment with insulin alone. CONCLUSION: Insulin has protective effects on rat hepatocytes injury indirectly induced by LPS, which is associated with suppression of the pro-inflammatory cytokine TNF-alpha and increment of the anti-inflammatory cytokine IL-10 both from Kupffer cells.

Animals↗

PubMed2006

[Research on the progress of neuroprosthesis for the limb motor system].

This paper reviews the current developing situation of neuroprostheses which are based on the functional electrical stimulation (FES) technique and are used to provide limb movements. It also discusses the major challenges of neuroprostheses, which will be faced in the future development and in the clinical applications for the rehabilitation of spinal cord injury and stroke.

Electric Stimulation Therapy↗

PubMed2006

[Oxaliplatin in combination with calcium folinate and fluorouracil as neoadjuvant chemotherapy in the treatment of advanced gastric cancer].

OBJECTIVE: To evaluate the efficacy and toxicity of oxaliplatin in combination with calcium folinate and fluorouracil (OXA-LV5FU2) regimen as the neoadjuvant chemotherapy in the treatment of patients with advanced gastric cancer. METHODS: Twenty-seven patients were treated with OXA-LV5FU2 before operation. Neoadjuvant chemotherapy regimens containing OXA 100 mg/m(2) iv 2 h d1, LV 200 mg/m(2) iv 2 h followed by 5-FU 400 mg/m(2) iv bolus and 5-FU 1 g/m(2) iv 48-72 h d1, 2 were administered every 2 to 3 weeks for 3 to 4 cycles before local treatment. The responses of the primary tumor and the chemotherapy toxicity were observed in each patient. RESULTS: Twenty-four patients were treated with surgery. The radical resections were carried out in 14 cases. The overall clinical efficacy rate was 48.1% with 3.7% CR and 44.4% PR, SD was 33.3% and PD was 18.5%. Eight of the 27 cases were downstaged. The common toxicities were nausea, vomiting, peripheral neuropathy, leukocytopenia, alopecia and hepatosis. The toxicities relieved after symptomatic treatment. There was no relative risk of death during treatment. CONCLUSION: OXA-LV5FU2 is a very effective and well tolerated regimen as neoadjuvant chemotherapy for advanced gastric cancer.

Adult↗

PubMed2006

[Correlation of hyponatremia with plasma renin activity, antidiuretic hormone and brain natriuretic peptide in chronic heart failure].

OBJECTIVE: To observe the changes of plasma renin activity, antidiuretic hormone and brain natriuretic peptide in chronic heart failure (CHF) and their correlation with hyponatremia. METHODS: Plasma levels of PRA, ADH, and BNP were measured by radioimmunology in 76 CHF patients. Forty-one out of 76 CHF patients with hyponatremia and 35 CHF patients without hyponatremia were identified by serum sodium. The rates of rehospitalization within 3 months were compared in two groups. RESULTS: Levels of plasma renin activity, ALD, and BNP in CHF patients with hyponatremia were notably higher than those in patients without hyponatremia classified by New York Heart Association (NYHA) grade II - IV: PRA [(2.7 +/- 1.0) ng.ml(-1).h(-1) vs. (1.8 +/- 0.7) ng.ml(-1).h(-1), (4.3 +/- 1.2) ng.ml(-1).h(-1) vs. (3.0 +/- 0.9) ng.ml(-1).h(-1), (5.6 +/- 1.3) ng.ml(-1).h(-1) vs. (3.5 +/- 1.1) ng.ml(-1).h(-1), respectively, P < 0.05], ADH [(59.7 +/- 17.4) ng/L vs. (48.6 +/- 15.3) ng/L, (68.4 +/- 17.6) ng/L vs. (56.3 +/- 19.2) ng/L, (75.3 +/- 20.0) ng/L vs. (51.4 +/- 16.2) ng/L, respectively, P < 0.05] and BNP [(276.4 +/- 75.2) ng/L vs. (185.3 +/- 55.3) ng/L, (380.1 +/- 113.6) ng/L vs. (258.5 +/- 62.1) ng/L, (564.0 +/- 125.2) ng/L vs. (405.3 +/- 102.9) ng/L, respectively, P < 0.05]. In the simple regression analyses, hyponatremia was negative correlated with PRA, ADH and BNP (r = -0.31, P < 0.05; r = -0.28, P < 0.05, r = -0.80, P < 0.01). The rate of rehospitalization within 3 months in hyponatremia group was higher than that in control group. CONCLUSIONS: There is relation of hyponatremia to the changes of plasma renin activity, antidiuretic hormone and brain natriuretic peptide in chronic heart failure. Hyponatremia may accelerate the excretion of plasma PRA, ADH and BNP in chronic heart failure. Neuroendocrine activation in patients of congestive heart failure with hyponatremia is higher than that of normal natremia group.

Aged↗

PubMed2005

In situ detection of specific DNA double strand breaks using rolling circle amplification.

We have developed a method to localize DNA double strand breaks (DSBs) in situ in cultured mammalian cells. Adenoviruses encoding Saccharomyces cerevisiae HO endonuclease and its cleavage site were used to induce site-specific DSBs. Rolling circle amplification (RCA), a sensitive method that allows the detection of single molecular event by rapid isothermal amplification, was used to localize the broken ends in situ. Punctate RCA signals were only seen in the cells that had been infected with both adenoviruses encoding HO endonuclease and HO cleavage site, but not in the cells mock-infected or infected with the site or endonuclease virus only. With use of a chemical crosslinker, in situ RCA and immunofluorescence (IF) can be performed simultaneously on the same sample. This methodology provides a novel approach for investigation of DNA recombination, DNA repair, and checkpoint controls in mammalian cells.

Adenoviridae↗

PubMed2005

Vasculoprotective effect of insulin in the ischemic/reperfused canine heart: role of Akt-stimulated NO production.

OBJECTIVES: The objectives of this study were to investigate the vasculoprotective effects of glucose-insulin-potassium (GIK) on ischemia/reperfusion-induced coronary endothelial functional injury and to elucidate the mechanism involved. METHODS: Dogs were subjected to 50 min of coronary occlusion and 4 h of reperfusion. Vehicle, GIK, or GK were intravenously infused 5 min before reperfusion, and the coronary vascular dysfunction and endothelial apoptosis were determined. In a separate study, cultured endothelial cells were subjected to simulated ischemia/reperfusion, and the signaling pathway involved in insulin's anti-apoptotic effect was investigated. RESULTS: In vivo ischemia/reperfusion caused significant coronary vascular endothelial dysfunction as evidenced by reduced endothelium-dependent vasorelaxation, decreased nitric oxide (NO) production, and endothelial cell apoptosis as determined by caspase 3 activation and TUNEL staining. Treatment with GIK, but not GK, markedly improved the endothelium-dependent coronary vasorelaxation (P<0.01 versus vehicle), increased total NO production (P<0.01), and attenuated endothelial apoptosis. In cultured endothelial cells, treatment with insulin also markedly increased NO production and reduced simulated ischemia/reperfusion-induced apoptosis. Moreover, pre-treatment with either Akt inhibitor or NO synthase inhibitor almost abolished the anti-apoptotic effect exerted by insulin but not by SNAP, an NO donor. CONCLUSION: These results demonstrate that in vivo treatment with GIK at reperfusion attenuates ischemia/reperfusion-induced coronary endothelial dysfunction and endothelial apoptosis in an Akt-dependent and NO-mediated fashion. The coronary vasculoprotective effect elicited by insulin may contribute to the previously observed cardiac protective effect of GIK.

Acetylcholine↗

PubMed2005

Identification of potent type I MetAPs inhibitors by simple bioisosteric replacement. Part 2: SAR studies of 5-heteroalkyl substituted TCAT derivatives.

Systematic SAR studies on the thiazole ring 5-substituent of TCAT derivatives revealed that the introduction of a beta-alkoxy or an amino group enhanced the inhibitory activity significantly. The present compounds are representative of specific Co(II)-MetAP1 inhibitors. Before the physiologically relevant metal ions for MetAPs are established, these small molecular compounds could be used as tools for detailed biological studies.

Alkylation↗

PubMed2005

DNA damage regulates Chk2 association with chromatin.

DNA damage triggers cellular signaling pathways that control the cell cycle and DNA repair. Chk2 is a critical mediator of diverse responses to DNA damage. Chk2 transmits signals from upstream phosphatidylinositol 3'-kinase-like kinases to effector substrates including p53, Brca1, Cdc25A, and Cdc25C. Using chromatin fractionation as well as immunostaining combined with detergent pre-extraction, we have found that a small pool of Chk2 is associated with chromatin prior to DNA damage. Recovery of chromatin-bound Chk2 is reduced in an ATM-dependent manner by exposure to ionizing radiation. Camptothecin and adriamycin also reduce the amount of chromatin-associated Chk2. The Thr(68)-phosphorylated forms of Chk2 induced by DNA damage are found in soluble fractions, but not in the chromatin-enriched fraction. Functional serine/threonine glutamine cluster domain, forkhead-associated domain, and kinase activity are all required for efficient reduction of chromatin-bound Chk2 in response to DNA damage. Artificial induction of Chk2 oligomerization concomitant with exposure to low dose ionizing radiation reduces chromatin-bound Chk2. When Chk2 is incubated with chromatin-enriched fractions in vitro in the presence of ATP, hyperphosphorylated forms of Chk2 bind more weakly to chromatin than hypophosphorylated forms. Taken together, our data suggest that DNA damage induces activation of chromatin-bound Chk2 by a chromatin-derived signal, and that this results in dissociation of activated Chk2 from chromatin, facilitating further signal amplification and transmission to soluble substrates.

Ataxia Telangiectasia Mutated Proteins↗

PubMed2005

Arabidopsis BRS1 is a secreted and active serine carboxypeptidase.

The Arabidopsis BRS1 gene encodes a serine carboxypeptidase II-like protein. Its biological role in the brassinosteroid signaling pathway was first established by its capability to specifically suppress a weak brassinosteroid insensitive 1 (bri1) allele, bri1-5, when overexpressed. To gain additional insights into the molecular mechanisms of BRS1 function, the subcellular localization and the biochemical characteristics of BRS1 were determined by using transgenic plants harboring a 35S-BRS1-GFP construct and fusion proteins purified from 35S-BRS1-FLAG transgenic plants. The BRS1-GFP protein was mainly secreted and accumulated in the extracellular space. Immunological data suggest that BRS1 is proteolytically processed by an unknown endoproteinase in planta. Affinity-purified BRS1-FLAG from transgenic plants show strong hydrolytic activity with a broad P1 substrate preference including basic and hydrophobic groups on either side of the scissile bond. The hydrolytic activity of BRS1 can be strongly inhibited by a serine protease inhibitor, phenylmethylsulfonyl fluoride. The pH and temperature optima for the hydrolytic activity of BRS1 are pH 5.5 and 50 degrees C, respectively. These data demonstrate that BRS1 is a secreted and active serine carboxypeptidase, consistent with the hypothesis suggested by our previous genetic evidence that BRS1 may process a protein involved in an early event in the BRI1 signaling pathway.

Alleles↗

PubMed2005

DNA biosensor based on chitosan film doped with carbon nanotubes.

A biosensor based on chitosan doped with carbon nanotube (CNT) was fabricated to detect salmon sperm DNA. Methylene blue (MB) was employed as a DNA indicator. It was found that CNTs can enhance the electroactive surface area threefold (0.28 +/- 0.03 and 0.093 +/- 0.06 cm(2) for chitosan-CNT- and chitosan-modified electrodes, respectively) and can accelerate the rate of electron transfer between the redox-active MB and the electrode. A low detection limit of 0.252 nM fish sperm DNA was achieved, and no interference was found in the presence of 5 microg/ml human serum albumin. The differential pulse voltammetry signal of MB was linear over the fish sperm DNA concentration range of 0.5-20 nM.

Animals↗

PubMed2005

Identification of potent type I MetAP inhibitors by simple bioisosteric replacement. Part 1: Synthesis and preliminary SAR studies of thiazole-4-carboxylic acid thiazol-2-ylamide derivatives.

A series of thiazole-4-carboxylic acid thiazol-2-ylamide (TCAT, 4) derivatives were designed and synthesized according to simple bioisosteric replacement from previously reported pyridine-2-carboxylic acid thiazol-2-ylamide (PCAT) MetAP inhibitors. The preliminary SAR studies demonstrated that these TCAT series of compounds showed different activity and selectivity compared with those of the corresponding PCAT compounds. These findings provide useful information for the design and discovery of more potent inhibitors of type I MetAPs.

Aminopeptidases↗

PubMed2005

Discovery of novel inhibitor of human leukocyte common antigen-related phosphatase.

Human leukocyte common antigen-related phosphatase (LAR) may play a role in type 2 diabetes and cancer, and in the development of the nervous system, and it may be an attractive target for the treatment of diabetes and cancer. We identified eight hits from the random screening of LAR D1 with a high-throughput screening assay. Further validation of the eight hits showed that the meD insertion was associated with inhibition of LAR D1D2 and LAR D1Q. These data suggest that the inserted meD peptide influences the interaction of the enzyme and inhibitor, which is consistent with the kinetic catalysis constants of the substrate pNPP. Our data showed that Hit 1, the first published novel inhibitor of LAR, is a competitive inhibitor with a K(i) of 330 nM that displays obvious selectivity for LAR and mouse PTPsigma, but not for other protein tyrosine phosphatases.

Animals↗

PubMed2005

Remote ischemic preconditioning of the recipient reduces myocardial ischemia-reperfusion injury of the denervated donor heart via a Katp channel-dependent mechanism.

BACKGROUND: We assess whether remote ischemic preconditioning (rIPC) of the recipient can modify ischemia-reperfusion (IR) injury in the donor heart following orthotopic heart transplantation from brain dead donors and to examine potential mechanisms of protection. METHODS: Sixteen pigs weighing from 26 to 34.2 (mean 29.2) kg, randomized to control group (n=5), ischemic preconditioning (rIPC) group (n=6), and to receive rIPC with prior glibenclamide administration (Glib + rIPC) group (n=5) underwent orthotopic heart transplantation with the support of hypothermic (32 degrees C) cardiopulmonary bypass (CPB). The hearts were harvested from donor animal rendered brain dead by balloon compression via a craniotomy. Preconditioning of the recipients was induced by four 5-min cycles of lower limb ischemia. Myocardial infarction (MI) was induced following heart transplantation by 30 min of left anterior descending (LAD) artery occlusion following by 2 hr of regional reperfusion. The extent of myocardial infarction was assessed by triphenyltetrazolium (TTC) staining. RESULTS: Preconditioning of the recipient reduced the mass of MI (6.75+/-6.3 g in rIPC vs. 18.1+/-5.8 g in control, P=0.01), MI to area at risk (ARR) mass ratio by 57% (15.6%+/-15.2% vs. 36.3%+/-13.4%, P=0.04). The protective effect of preconditioning was abolished by pretreatment with glibenclamide. CONCLUSIONS: Remote ischemic preconditioning of the recipient, decreases ischemia-reperfusion injury in the brain dead donor heart following orthotopic heart transplantation via a Katp channel-dependent mechanism. This study suggests that a circulating effector persists after the rIPC stimulus is applied, and excludes an ongoing afferent neurogenic mechanism of cardioprotection.

Animals↗

PubMed2005

Study on the interaction between DNA and protein induced by anticancer drug carboplatin.

The interaction of DNA and human serum albumin (HSA) in the presence of anticancer drug carboplatin was studied with piezoelectric quartz crystal impedance (PQCI) and electrochemistry techniques. In the PQCI analysis, the correlative parameters including the frequency (f0), the motional resistance (R(m)), and the static capacitance (C0) in the experiment were obtained and discussed in detail. Additionally, the kinetics parameters of the cross-linking process were investigated and a response kinetics model was deduced. The values of association rate constant k1, dissociation rate constant k(-1) and the reaction equilibrium constant K were estimated to be 1.895 mg/ml(-1) s(-1), 4.7 x 10(-5) s(-1) and 4.03 x 10(4) (mg/ml)-1, respectively. Furthermore, cyclic voltammetry (CV) and electrochemical AC impedance techniques were employed to testify the cross-linking process.

Carboplatin↗

PubMed2005

Identification and functional analysis of in vivo phosphorylation sites of the Arabidopsis BRASSINOSTEROID-INSENSITIVE1 receptor kinase.

Brassinosteroids (BRs) regulate multiple aspects of plant growth and development and require an active BRASSINOSTEROID-INSENSITIVE1 (BRI1) and BRI1-ASSOCIATED RECEPTOR KINASE1 (BAK1) for hormone perception and signal transduction. Many animal receptor kinases exhibit ligand-dependent oligomerization followed by autophosphorylation and activation of the intracellular kinase domain. To determine if early events in BR signaling share this mechanism, we used coimmunoprecipitation of epitope-tagged proteins to show that in vivo association of BRI1 and BAK1 was affected by endogenous and exogenous BR levels and that phosphorylation of both BRI1 and BAK1 on Thr residues was BR dependent. Immunoprecipitation of epitope-tagged BRI1 from Arabidopsis thaliana followed by liquid chromatography-tandem mass spectrometry (LC/MS/MS) identified S-838, S-858, T-872, and T-880 in the juxtamembrane region, T-982 in the kinase domain, and S-1168 in C-terminal region as in vivo phosphorylation sites of BRI1. MS analysis also strongly suggested that an additional two residues in the juxtamembrane region and three sites in the activation loop of kinase subdomain VII/VIII were phosphorylated in vivo. We also identified four specific BAK1 autophosphorylation sites in vitro using LC/MS/MS. Site-directed mutagenesis of identified and predicted BRI1 phosphorylation sites revealed that the highly conserved activation loop residue T-1049 and either S-1044 or T-1045 were essential for kinase function in vitro and normal BRI1 signaling in planta. Mutations in the juxtamembrane or C-terminal regions had only small observable effects on autophosphorylation and in planta signaling but dramatically affected phosphorylation of a peptide substrate in vitro. These findings are consistent with many aspects of the animal receptor kinase model in which ligand-dependent autophosphorylation of the activation loop generates a functional kinase, whereas phosphorylation of noncatalytic intracellular domains is required for recognition and/or phosphorylation of downstream substrates.

Arabidopsis↗