Biomedical subjects

Hua Liu

Publications and source records attributed to Hua Liu.

At least 73 records · Page 4Linked to original sources

PubMed2004

Identification of the antivasopermeability effect of pigment epithelium-derived factor and its active site.

Vascular permeability plays a key role in a wide array of life-threatening and sight-threatening diseases. Vascular endothelial growth factor can increase vascular permeability. Using a model system for nonproliferative diabetic retinopathy, we found that pigment epithelium-derived factor (PEDF) effectively abated vascular endothelial growth factor-induced vascular permeability. A 44-amino acid region of PEDF was sufficient to confer the antivasopermeability activity. Additionally, we identified four amino acids (glutamate-101, isoleucine-103, leucine-112, and serine-115) critical for this activity. PEDF, or a derivative, could potentially abate or restore vision loss from diabetic macular edema. Furthermore, PEDF may represent a superior therapeutic approach to sepsis-associated hypotension, nephrotic syndrome, and other sight-threatening and life-threatening diseases resulting from excessive vascular permeability.

Amino Acid Sequence↗

PubMed2004

Perturbation of conjugation in allylic lithium compounds due to stereochemical control of internal lithium coordination: crystallography, NMR, and calculational studies.

Several allylic lithium compounds have been prepared with ligands tethered at C(2). These are with (CH(3)OCH(2)CH(2))(2)NCH(2)-, 6, 1-TMS 5, 1,3-bis(TMS) 8, and 1,1,3-tris(TMS) 9. Allylic lithiums with (CH(3)OCH(2)CH(2))(2)NCH(2)C(CH(3))(2)-, are 10, 1-TMS 11, and 1,3-bis(TMS), 12 compounds with -C(CH(3))(2)CH(2)N-((S)-(2-methoxymethyl)-pyrrolidino) at C(2) 13, 1-TMS 14, and 1,3-bis(TMS) 15. In the solid state, 8-10 and 12 are monomers, 6 and 13 are Li-bridged dimers, and 5 and 7 are polymers. In solution (NMR data), 5, 7-12, 14, and 15 are monmeric, and 6 is a dimer. All samples show lithium to be closest to one of the terminal allyl carbons in the crystal structures and to exhibit one-bond (13)C-(7)Li or (13)C(1)-(7)Li spin coupling, for the former typically ca. 3 Hz and for the latter 6-8 Hz. In every structure, the C(1)-C(2) allyl bond is longer than the C(2)-C(3) bond, and both lie between those for solvated delocalized and unsolvated localized allylic lithium compounds, respectively, as is also the case for the terminal allyl (13)C NMR shifts. Lithium lies 40-70 degrees off the axis perpendicular to the allyl plane at C(1). These effects are variable, so the trend is that the differences between the C(1)-C(2) and C(2)-C(3) bond lengths, (13)delta(3)-(13)delta(1) values, and the (13)C(1)-(7)Li or (13)C-(6)Li coupling constants all increase with decreasing values of the torsional angle that C(1)-Li makes with respect to the allyl plane.

Journal Article↗

PubMed2004

[Studies on the transfection of umbilical endothelia with catalytic subunit of telomerase].

OBJECTIVE: To investigate the variety of proliferating ability of umbilical endothelia (UE) transfected by plasmid pBABE-HYGR-hTERT. METHODS: UE was identified from two aspects: morphology and CD34 labeling technique. The plasmid was obtained and identified by alkali splitting and gel electrophoresis. Liposomes were used to transfect UE. RT-PCR based telomeric repeat amplification protocol (TRAP) assay was used to measure the telomerase activity of endothelia. RESULTS: UE arranged as "cobblestone" and were positive of CD34 labeling. Endothelia transfected by pBABE-HYGR-hTERT(HC) had an raised absorbance of 0.889. The shape of growth curve of HC was similar to UE. But the absorbance of MTT test and the amount of HC were prior to UE at every measuring time and the amount of HC increased four times within 8 days (P < 0.05). CONCLUSION: The transfection of pBABE-HYGRO-hTERT had greatly improved the proliferating abilities and activated the telomerase of UE.

Catalytic Domain↗

PubMed2004

[Genetic polymorphisms of six short tandem repeat loci in the Han population of Henan province in China].

OBJECTIVE: To investigate the allele frequencies of six short tandem repeats (STR) loci D12S391, D5S818, D18S51, PAHI3, D8S1179, D3S1358 in the Han population of Henan province and to obtain preliminary data. METHODS: DNA was extracted with phenol-chloroform from 140 EDTA-blood specimens of healthy unrelated individuals in Henan population; multiplex PCR technique and PAGE vertical electrophoresis were used to screen the genotype frequencies of six STR systems in Henan population. RESULTS: The test for Hardy-Weinberg equilibrium revealed that the genotype distribution was correspondent with the expected. The observed heterozygosities of six loci were 0.871, 0.769, 0.871, 0.773, 0.901, 0.722. The calculated discrimination power is 0.9999998, the calculated power of exclusion is 0.99845, the calculated matching probability is 2.39 x 10(-7). CONCLUSION: All of the six loci in this study have high power of discrimination and exclusion; they may be very useful genetic markers for individual identification, paternity test and genetics purposes.

Alleles↗

PubMed2004

[Study on cultivating technology of high yield and quality of Plantago asiatica of Jiangxi geo-herbalism].

OBJECTIVE: To study the high-yield and high-quality cultivating technology of Plantago asiatica, adapt to the demands of GAP. METHOD: The main factors which influenced the yield and quality in the production process of P. asiatica was studied. RESULT: The standard system cultivating technology of high yield and quality of P. asiatica was established. CONCLUSION: The seeds of P. asiatica can reach the objective of high yield and high quality on the basis of this cultivating technology.

China↗

PubMed2003

Cytochrome P450 2E1 null mice provide novel protection against cisplatin-induced nephrotoxicity and apoptosis.

BACKGROUND: Reactive oxygen metabolites (ROM) are important mediators of cisplatin-induced nephrotoxicity and apoptosis. The site and source of generation of these metabolites are not well defined. Cytochrome P450 (CYP) are heme-containing enzymes that can generate ROM during the oxidative metabolism of exogenous and endogenous compounds. CYP2E1 was identified and localized to the kidney proximal tubule. There is evidence to suggest that CYP2E1 is involved in the generation of ROM. METHODS: The current study was performed utilizing CYP2e1 null mice (CYP2e1-/-). Cisplatin nephrotoxicity was induced in mice by single intraperitoneal injection of cisplatin and animals were sacrificed 72 hours later. Renal function was assessed and various biochemical tests were performed, including histologic studies. RESULTS: CYP2e1-/- demonstrated marked functional and histologic protection against cisplatin-induced renal injury. Incubation of CYP2e1-/- kidney slices with cisplatin resulted in significant decrease in the generation of ROM and attenuation of cytotoxicity as compared to that of wild-type mice (CYP2e1+/+). Cisplatin-induced apoptosis was also markedly reduced in the CYP2e1-/- mice. Direct incubation of cisplatin with the microsomes isolated from CYP2e1-/- kidney cortex produced significant decrease in the generation of hydrogen peroxide, catalytic iron content, and hydroxyl radical formation compared to CYP2e1+/+ microsomes. CONCLUSION: Our results thus demonstrate a pivotal role of CYP2E1 in cisplatin-induced nephrotoxicity and apoptosis. We postulate that the interaction of cisplatin with CYP2E1 results in the generation of ROM that causes renal injury and initiates apoptosis.

Animals↗

PubMed2003

Role of cytochrome P450 2B1 in puromycin aminonucleoside-induced cytotoxicity to glomerular epithelial cells.

Puromycin aminonucleoside (PAN)-induced glomerular injury in rats mimics minimal-change nephrotic syndrome (NS) in humans. We have demonstrated an important role of cytochrome P450 (CYP) as a significant source of catalytic iron in this model of NS. The current study was designed to identify CYP isozyme(s) present in the rat glomerular epithelial cells (GEC) and to explore the role of the specific CYP isozyme in PAN-induced cytotoxicity. CYP2B1 was identified in GEC by immunocytochemistry and Western blot. Treatment of GEC with PAN resulted in a marked generation of hydrogen peroxide (H(2)O(2)) and reduction of CYP2B1 content associated with significant increase in catalytic iron and hydroxyl radical formation. Preincubating GEC with CYP2B1 inhibitors (piperine and cimetidine) and H(2)O(2) scavenger (pyruvate) significantly reduced H(2)O(2 )generation, preserved CYP2B1 content, prevented the increase in catalytic iron and hydroxyl radical formation including PAN-induced cytotoxicity. We also observed the induction of heme oxygenase (HO-1) in PAN-treated GEC, and this up-regulation was reduced by pretreatment of the CYP inhibitors and pyruvate. Our data thus indicate an important role of CYP2B1 in PAN-induced cytotoxicity by serving as a site of reactive oxygen metabolite generation and a significant source of catalytic iron.

Animals↗

PubMed2003

[Protective effects and mechanisms of serial TCM "Huoxuehuayu" prescriptions on cerebral ischemia-reperfusion injury in rats].

OBJECTIVE: To determine effects and mechanisms of traditional Chinese medicine serial "Huoxuehuayu" (activating blood flow and removing blood stasis) prescriptions on cerebral ischemia-reperfusion injury in rats. METHODS: Focal cerebral ischemia was induced by 60 min of middle cerebral artery occlusion (MCAO) and followed by 3 d reperfusion. Drugs were orally administered 1 h before MCAO and 4 h after reperfusion and the following 2 d. The neurological scores were evaluated 3 d after reperfusion. Then the animals were sacrificed, the infarct volumes, right and left areas of brain section, the pathologic changes and the normal neurons in hippocampal CA1 and cortex were determined by using an image analyzer. Nitric oxide synthase (NOS), superoxide dismutase (SOD) activities and malondialdehyde (MDA) content in brain tissue were evaluated by spectrophotography. The expression of NMDA R1 subunit (NR1) and endothelial NOS (eNOS) was determined by immunoblotting technique. RESULT: Serial "Huoxuehuayu" prescriptions and nimodipine improved neuronal dysfunction, and reduced infarct size and brain edema. Serial Huoxuehuayu prescriptions and nimodipine reduced MDA content and NOS activity, and increased SOD activity. Western blotting analysis demonstrated induction of NR1. CONCLUSION: Serial Huoxuehuayu prescriptions have a protective effect on cerebral ischemia-reperfusion injury by reducing NOS activity, MDA content, expression of NR1 and increasing SOD activity.

Animals↗

PubMed2002

Ephrin-B1 transduces signals to activate integrin-mediated migration, attachment and angiogenesis.

Ephrin-B/EphB family proteins are implicated in bidirectional signaling and were initially defined through the function of their ectodomain sequences in activating EphB receptor tyrosine kinases. Ephrin-B1-3 are transmembrane proteins sharing highly conserved C-terminal cytoplasmic sequences. Here we use a soluble EphB1 ectodomain fusion protein (EphB1/Fc) to demonstrate that ephrin-B1 transduces signals that regulate cell attachment and migration. EphB1/Fc induced endothelial ephrin-B1 tyrosine phosphorylation, migration and integrin-mediated (alpha(v)beta(3) and alpha(5)beta(1)) attachment and promoted neovascularization, in vivo, in a mouse corneal micropocket assay. Activation of ephrin-B1 by EphB1/Fc induced phosphorylation of p46 JNK but not ERK-1/2 or p38 MAPkinases. By contrast, mutant ephrin-B1s bearing either a cytoplasmic deletion (ephrin-B1DeltaCy) or a deletion of four C-terminal amino acids (ephrin-B1DeltaPDZbd) fail to activate p46 JNK. Transient expression of intact ephin-B1 conferred EphB1/Fc migration responses on CHO cells, whereas the ephrin-B1DeltaCy and ephrin-B1DeltaPDZbd mutants were inactive. Thus ephrin-B1 transduces 'outside-in' signals through C-terminal protein interactions that affect integrin-mediated attachment and migration.

Amino Acid Sequence↗

PubMed2002

Cytochrome P450 2B1 mediates oxidant injury in puromycin-induced nephrotic syndrome.

BACKGROUND: Reactive oxygen metabolites (ROM) are important mediators of puromycin aminonucleoside (PAN) induced minimal change nephrotic syndrome (NS) in rats. We have recently shown that cytochrome P450 (CYP) is a significant source of catalytic iron in this model of glomerular injury. The current study was designed to identify the CYP isozyme(s) in the rat glomeruli and explore the role of the specific isozyme(s) in PAN-induced minimal change NS. METHODS: NS was induced in rats by a single intravenous injection of PAN. Animals were sacrificed at different time points for variety of biochemical assays including Western blot, immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). Ultrastructural histochemistry was utilized to study hydrogen peroxide (H2O2) generation in the kidney. RESULTS: Several CYP isozymes were tested and CYP2B1 was localized exclusively in the rat glomeruli but not in the tubules. Treatment with PAN resulted in the generation of H2O2 in the glomerular basement membrane with significant loss of CYP2B1 content accompanied by a marked increase in the catalytic iron. CYP2B1 inhibitors cimetidine and piperine significantly reduced H2O2 generation, and prevented the loss of CYP2B1 content and the increase in the catalytic iron. CYP2B1 inhibitors also provided significant protection against PAN induced proteinuria. The induction of heme oxygenase and ferritin also was observed in the glomeruli in PAN-treated rats. Both cimetidine and piperine reduced the up-regulation of these proteins. CONCLUSION: Our data indicate that CYP2B1 plays an important role in PAN induced NS by serving as a site for ROM generation and a significant source of catalytic iron.

Animals↗

PubMed2002

Potential role for Duffy antigen chemokine-binding protein in angiogenesis and maintenance of homeostasis in response to stress.

CXC chemokines, which induce angiogenesis, have glutamine-leucine-arginine amino acid residues (ELR motif) in the amino terminus and bind CXCR2 and the Duffy antigen chemokine-binding protein. Duffy, a seven transmembrane protein that binds CXC and CC chemokines, has not been shown to couple to trimeric G proteins or to transduce intracellular signals, although it is highly expressed on red blood cells, endothelial cells undergoing neovascularization, and neuronal cells. The binding of chemokines by Duffy could modulate chemokine responses positively or negatively. Positive regulation could come through the presentation of chemokine to functional receptors, and negative regulation could come through Duffy competition with functional chemokine receptors for chemokine binding, thus serving as a decoy receptor. To determine whether Duffy has a role in angiogenesis and/or maintenance of homeostasis, we developed transgenic mice expressing mDuffy under the control of the preproendothelin promoter/enhancer (PPEP), which directs expression of the transgene to the endothelium. Two PPEP-mDuffy-transgenic founders were identified, and expression of the transgene in the endothelium was verified by Northern blot, RT-PCR, and immunostaining of tissues. The phenotype of the mice carrying the transgene appeared normal by all visual parameters. However, careful comparison of transgenic and nontransgenic mice revealed two phenotypic differences: mDuffy-transgenic mice exhibited a diminished angiogenic response to MIP-2 in the corneal micropocket assay, and mDuffy-transgenic mice exhibited enhanced hepatocellular toxicity and necrosis as compared with nontransgenic littermates in response to overdose of acetaminophen (APAP; 400 mg/kg body weight). Morover, APAP treatment was lethal in 50% of the mDuffy-transgenic mice 24 h post challenge, and 100% of the nontransgenic littermates survived this treatment at the 24 h time point. Our data suggest that enhanced expression of mDuffy on endothelial cells can lead to impaired angiogenic response to chemokines and impaired maintenance of homeostasis in response to toxic stresses.

Acetaminophen↗

PubMed2002

[Research on the forecast of intraocular lens power after excimer laser keratorefractive operation].

OBJECTIVE: To study the accuracy of different formulas forecasting intracellular lens (IOL) power after excimer laser keratorefractive operation. METHODS: One hundred and twenty eyes (60 cases) underwent LASIK surgery. Before and after the surgery, the IOL powers were calculated to correct the myopia to emmetropia by experiential SRK II formula, theoretical SRK/T formula and Binkhoist II formula respectively. Then we calculated the IOL power equal to original lens power by F, and analyzed the results before and after surgery by SPSS statistical software. RESULTS: 1. The IOL powers were not obviously different by different formulas between pre-operative and post-operative results in low myopia (P > 0.05). In middle and high myopia there were obvious differences (P < 0.01), the postoperative results were smaller than the preoperative ones. 2. The differences of equal IOL power by different formulas were highly related to the practical corrective refractive values of the surgery. Regression formula: The difference of equal IOL power = a + b x the practical corrective refractive value of the surgery. (SRK II: a = -l.23, b = 0.72; SRK/T: a = -l.03, b = 0.52; Binkhoist II: a = -1.44, b = 0.5). CONCLUSION: The IOL powers forecasted by different formulas are smaller in middle and high myopia after excimer laser keratorefractive operation than that before the operation, and can be corrected by regression formula.

Adolescent↗

PubMed2002

Blockade of EphA receptor tyrosine kinase activation inhibits vascular endothelial cell growth factor-induced angiogenesis.

Angiogenesis is a multistep process involving a diverse array of molecular signals. Ligands for receptor tyrosine kinases (RTKs) have emerged as critical mediators of angiogenesis. Three families of ligands, vascular endothelial cell growth factors (VEGFs), angiopoietins, and ephrins, act via RTKs expressed in endothelial cells. Recent evidence indicates that VEGF cooperates with angiopoietins to regulate vascular remodeling and angiogenesis in both embryogenesis and tumor neovascularization. However, the relationship between VEGF and ephrins remains unclear. Here we show that interaction between EphA RTKs and ephrinA ligands is necessary for induction of maximal neovascularization by VEGF. EphA2 RTK is activated by VEGF through induction of ephrinA1 ligand. A soluble EphA2-Fc receptor inhibits VEGF-, but not basic fibroblast growth factor-induced endothelial cell survival, migration, sprouting, and corneal angiogenesis. As an independent, but complementary approach, EphA2 antisense oligonucleotides inhibited endothelial expression of EphA2 receptor and suppressed ephrinA1- and VEGF-induced cell migration. Taken together, these data indicate an essential role for EphA receptor activation in VEGF-dependent angiogenesis and suggest a potential new target for therapeutic intervention in pathogenic angiogenesis.

Angiogenesis Inhibitors↗

PubMedDate not supplied

Reduced mitotic activity at the periphery of human embryonic stem cell colonies cultured in vitro with mitotically-inactivated murine embryonic fibroblast feeder cells.

This study attempted to investigate whether different levels of mitotic activity exist within different physical regions of a human embryonic stem (hES) cell colony. Incorporation of 5-bromo-2-deoxyuridine (BrdU) within newly-synthesized DNA, followed by immunocytochemical staining was used as a means of detecting mitotically-active cells within hES colonies. The results showed rather surprisingly that the highest levels of mitotic activity are primarily concentrated within the central regions of hES colonies, whereas the peripheral regions exhibited reduced levels of cellular proliferation. Two hypothetical mechanisms are therefore proposed for hES colony growth and expansion. Firstly, it is envisaged that the less mitotically-active hES cells at the periphery of the colony are continually migrating outwards, thereby providing space for newly-divided daughter cells within the more mitotically-active central region of the hES colony. Secondly, it is proposed that the newly-divided hES cells within the central region of the colony somehow migrate to the outer periphery. This could possibly explain why the periphery of hES colonies are less mitotically-active, since there would obviously be an extended time-lag before newly-divided daughter cells are ready again for the next cell division. Further investigations need to be carried out to characterize the atypical mechanisms by which hES colonies grow and expand in size.

Animals↗

PubMedDate not supplied

Culture media conditioned by heat-shocked osteoblasts enhances the osteogenesis of bone marrow-derived mesenchymal stromal cells.

Osteogenic cells differentiated from bone marrow-derived mesenchymal stromal cells (MSC) hold much promise in bone tissue engineering and reconstructive surgery. There is a dire need for well-defined and efficient protocols to promote the osteogenesis of ex vivo cultured MSC. Hence, this study investigated whether a combination of chemical stimuli (ascorbic acid, beta-glycerophosphate and dexamethasone) and culture media conditioned by a human foetal osteoblast cell line (hFOB) had any synergistic effect on the osteogenesis of MSC. Conditioned media with or without prior heat shock treatment (42 degrees C for 1 h) of the hFOB cell line, were collected and tested on rabbit MSC cultures, in the presence and absence of chemical stimuli. Osteogenic differentiation of MSC was assessed on both day 14 and 21 of ex vivo culture. The results showed conclusively that conditioned media promoted osteogenesis of MSC, which was further enhanced by prior heat shock-treatment of the hFOB cells, as well as by the presence of chemical stimuli. Among all experimental groups, the combination of culture medium conditioned by heat shocked hFOB cells together with chemical stimuli, exhibited the highest level of calcium mineralization, as assessed by Von Kossa staining. This provides clear evidence of a synergistic effect of conditioned media, heat shock and chemical stimuli. It is hoped that the data may contribute to the development of a more well-defined and efficient in vitro culture protocol to promote the osteogenesis of MSC for both clinical and non-clinical applications.

Animals↗

PubMedDate not supplied

Comparison of different test models for the assessment of cytotoxicity of composite resins.

This study compared the use of different test models to assess the cytotoxicity of a dental composite. The cytotoxicity of a composite polymerized using two halogen-based light-curing units (LCUs) (Max LC and Astralis) and two light-emitting diode LCUs (E-light and Freelight) served as the basis of comparison. Disk-shaped specimens (7 mm diameter, 2 mm high) were fabricated using the four different light sources. The specimens were used in several cytotoxicity test models: direct and indirect contact tests as well as an extract test with an established cell line L-929. The cells were stained with neutral red after cell-material contact for 48 h. Neutral red-stained areas (in mm2, for direct and indirect tests) and absorbance readings (for extract tests) were analysed statistically using ANOVA and the Tukey post hoc test, with P < 0.05 considered to be significantly different. Good correlation between direct and indirect contact tests (r = 0.903) was found. The extract test was the least correlated among the three tests. It was found that the E-light + Freelight-cured composite elicited cytotoxicity from the correlated studies. Uncured specimens were most detrimental to the cells in all tests. Our data demonstrated that composite cured with light-emitting diode LCUs were cytotoxic to L-929 cells. Different test models were found to give rise to different findings. Thus, a good cell-material contact method would replicate more closely the physiological situation in vivo. This in turn would give more clinically relevant results.

Animals↗

PubMedDate not supplied

Assignment of human sprouty 4 gene to chromosome segment 5q32 approximately 33 and analysis of its pattern of expression.

The human sprouty 4 (SPRY4) gene was localized to chromosome band 5q32 approximately 33 by screening the Stanford radiation hybrid G3 panel using a SPRY4-specific primer pair for PCR. Northern blot analysis revealed two different mRNAs (5 kb and 2 kb) in liver, skeletal muscle, heart, lung, kidney, spleen, placenta and small intestine. Reverse transcriptase-PCR analysis showed that SPRY4 was expressed in all tested tissues to different levels.

Blotting, Northern↗

PubMedDate not supplied

Inhibition of VEGF-dependent multistage carcinogenesis by soluble EphA receptors.

Elevated expression of Eph receptors has long been correlated with the growth of solid tumors. However, the functional role of this family of receptor tyrosine kinases in carcinogenesis and tumor angiogenesis has not been well characterized. Here we report that soluble EphA receptors inhibit tumor angiogenesis and tumor progression in vivo in the RIP-Tag transgenic model of vascular endothelial growth factor (VEGF)-dependent multistage pancreatic islet cell carcinoma. Soluble EphA receptors delivered either by a transgene or an osmotic minipump inhibited the formation of angiogenic islet, a premalignant lesion, and reduced tumor volume of solid islet cell carcinoma. EphA2-Fc or EphA3-Fc treatment resulted in decreased tumor volume but increased tumor and endothelial cell apoptosis in vivo. In addition, soluble EphA receptors inhibited VEGF and betaTC tumor cell-conditioned medium-induced endothelial cell migration in vitro and VEGF-induced cornea angiogenesis in vivo. A dominant negative EphA2 mutant inhibited--whereas a gain-of-function EphA2 mutant enhanced--tumor cell-induced endothelial cell migration, suggesting that EphA2 receptor activation is required for tumor cell-endothelial cell interaction. These data provide functional evidence for EphA class receptor regulation of VEGF-dependent tumor angiogenesis, suggesting that the EphA signaling pathway may represent an attractive novel target for antiangiogenic therapy in cancer.

Angiogenesis Inhibitors↗