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Biomedical subjects

Yan Zhang

Publications and source records attributed to Yan Zhang.

At least 469 records · Page 26Linked to original sources
PubMed2003

[Studies of hTERT gene expression in acute leukemia children].

OBJECTIVE: To explore the gene expression of human telomerase reverse transcriptase (hTERT) in acute leukemia (AL) children and its clinical implication. METHODS: Expression of hTERT mRNA was detected in K562 leukemia cell line, 40 acute leukemia children (AL) and 10 healthy subjects by reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS: hTERT gene was expressed in K562 cell line, acute lymphoblastic leukemia children (23/30), acute myeloid leukemia children (7/10), and healthy subject (1/10). The expression level of hTERT gene was observed in all subtypes of AL and was related to the prognosis of AL, and the patients with relative level > or = 1.0 were found to have lower complete remission (CR) rates and disease-free survival. CONCLUSION: hTERT gene expression is associated with the pathogenesis of childhood AL. It can serve as a prognostic indicator in childhood AL.

Adolescent↗
PubMed2003

[Chemical denitrification of nitrate from groundwater].

Batch experiments for catalytic reduction of nitrate from groundwater with Pd and/Cu catalysts were conducted. It was found that Pd-Cu combined catalysts at a ratio of 4 can maximize the nitrate reduction into nitrogen; above 80% total nitrogen removal efficiency was realized in this study. It was also found that the catalytic activity was affected by the amounts of catalysts, hydrogen flow rate and pressure, the initial concentration of nitrate. With an increasing in the amount of the catalysts, both nitrite and ammonia intermediates can be kept at a low level. A high flow rate and pressure of hydrogen was in favor of the catalytic reduction of nitrate, but not benefit for the selectivity. The catalytic reduction followed a first order kinetics in term of the initial nitrate concentration.

Ammonia↗
PubMed2003

Reduction of nitrate from groundwater: powder catalysts and catalytic membrane.

The reduction of nitrate contaminant in groundwater has gained renewed and intensive attention due to the environmental problems and health risks. Catalytic denetrification presents one of the most promising approaches for the removal of nitrate from water. Catalytic nitrate reduction from water by powder catalysts and catalytic membrane in a batch reactor was studied. And the effects of the initial concentration, the amounts of catalyst, and the flux H2 on the nitrate reduction were also discussed. The results demonstrated that nitrate reduction activity and the selectivity to nitrogen gas were mainly controlled by diffusion limitations and the mass transfer of the reactants. The selectivity can improved while retaining a high catalytic activity under controlled diffusion condition or the intensification of the mass transfer, and a good reaction condition. The total nitrogen removal efficiency reached above 80%. Moreover, catalytic membrane can create a high effective gas/liquid/solid interface, and show a good selectivity to nitrogen in comparative with the powder catalyst, the selectivity to nitrogen was improved from 73.4% to 89.4%.

Catalysis↗
PubMed2003

[Trabeculectomy with amniotic membrane transplantation and combining suture lysis of scleral flap in complicated glaucoma].

OBJECTIVE: To study and evaluate the outcome of trabeculectomy with amniotic membrane transplantation combining suture lysis of scleral flap in complicated glaucoma. METHODS: This operation was performed in 48 patients (67 eyes) with complicated glaucoma. Amniotic membrane was implanted under the scleral flap and the conjunctival flap and combined with suture lysis for scleral flap to control the outflow of the aqueous humor. RESULTS: Follow-up period ranged from 5 to 38 months (mean 19.5 months). The intraocular pressure (IOP) was lowered from (43.86 +/- 7.12) mm Hg (preoperative IOP) to postoperative (19.63 +/- 2.57) mm Hg (postoperative IOP) in neovascular glaucoma (t = 4.96, P < 0.001); from (40.31 +/- 4.79) mm Hg to (18.09 +/- 2.21) mm Hg in glaucoma after IOL implant (t = 3.54, P < 0.05); from (37.94 +/- 5.63) mm Hg to (20.14 +/- 3.15) mm Hg in aphakic glaucoma (t = 5.12, P < 0.05); from (32.48 +/- 3.98) mm Hg to (16.54 +/- 1.84) mm Hg in juvenile glaucoma (t = 4.23, P < 0.01); from (36.01 +/- 4.13) mm Hg to (18.11 +/- 3.40) mm Hg in uveitic glaucoma (t = 4.47, P < 0.01); from (34.43 +/- 5.28) mm Hg to (18.31 +/- 1.52) mm Hg in glaucoma after failure of conventional filtering operation (t = 2.05, P < 0.05). Statistical significant difference was found in the IOP before and after the operation. The rate of formation of functional bulb was 80.6%. There were no reject reaction and severe complications. CONCLUSION: Trabeculectomy with amniotic membrane transplantation combining suture lysis of scleral flap is a useful method in complicated glaucoma.

Adolescent↗
PubMed2003

[Relations between trace elements in drinking water and elderly residents' cognitive function].

The relationship between trace element levels in drinking water and cognitive function was studied for elderly residents in rural areas in China. Cognitive function was measured by a Chinese translation of the Community Screening Interview for Dementia (CSI "D"). The trace elements fluoride, calcium, selenium, aluminum, iron, zinc, cadmium, lead and arsenic contents of drinking water were determined using Chinese. National Standard Methods. A mixed effects model was used to evaluate the effect of each of the elements on cognitive function while adjusting for age, sex, and education level. Several of the elements examined had a significant effect on cognitive function when they were examined in a univariate context. However, after adjusting for other elements many of these results were not significant. There was a significant quadratic effect for calcium and a significant zinc-cadmium interaction. Cognitive function increased with calcium level to a certain point, and then decreased as calcium continued to increase. Zinc showed a positive relationship with cognitive function at low cadmium levels, but a negative relationship at high cadmium levels.

Aged↗
PubMed2003

[Expression, purification and identification of recombinant SARS coronavirus membrane protein].

A novel coronavirus (SARS-coronavirus, SARS-CoV) was discovered as the pathogen of the severe acute respiratory syndrome (SARS). According to studies with other coronaviruses, the membrane protein (M protein) is the main structural protein and the recombinant M protein may be useful as an antigen for detecting antibodies against coronavirus and for preparing vaccine. In this work, the M protein of SARS-CoV was expressed in E. coli as fusion protein with maltose binding protein at N-terminus and MxeGyrA intein CBD at C-terminus. The recombinant protein was identified by Western blot and mass spectrometry. The soluble parts of the cell crude extract were then partially purified by MBP affinity chromatography. The purified protein will be used for the studies on M protein's structure and the development of diagnostic method of SARS.

Amino Acid Sequence↗
PubMed2003

[Preperation of terbutaline sulphate pulsatile release tablet and mechanism elucidation].

AIM: To prepare terbutaline sulphate (TB) bi-layered pulsatile release tablets, evaluate the effects of the formulation and dissolution medium on drug release behavior, and to elucidate the mechanism of drug release based on obtained results. METHODS: Core tablets containing osmotic active agent were prepared by direct compression and spray coated with swelling layer and semipermeable membrane subsequently. Pharmaceutical properties of TB pulsatile tablets were investigated by dissolution test. The water uptake kinetics and swelling behavior of tablet were studied by the water uptake test and project enlargement method. RESULTS: TB released from bi-layered tablets in pulsatile behaviors. The lag-time was prolonged with the increase of coating level of semipermeable membrane and the steady release rate was increased significantly with the increase of osmotic active agent and swelling layer. It was shown that drug release behaviors were constant irrespective of various pH of dissolution medium and rotation speeds. All results indicated that diffusion, swelling and osmotic pumping were involved in the mechanism of drug release. CONCLUSION: Ideal pulsed release behaviors can be achieved by adjusting the coating level and composition of semipermeable membrane to meet the requirement of chronotherapy.

Administration, Oral↗
PubMed2003

[The inhibitive effect of tea polyphenols on oxidized low density lipoprotein intake in cultured rat mesangial cells].

OBJECTIVE: To study the inhibitive effect of tea polyphenols (TP) on oxidized low density lipoprotein (OX-LDL) intake in cultured rat mesangial cells. METHOD: Rat mesangial cells incubated in 80 mg.L-1 OX-LDL were treated with TP at different concentrations. Total cholesterol (TC) content of the mesangial cells and proportion of mesangial cells containing lipid droplets were measured, and ultrastructure observation was performed. RESULT: Foam cells were observed in mesangial cells stimulated by OX-LDL, and both the TC content and the proportion of lipid-droplet-containing cell were higher in these cells than in mesangial cells cultured in lipid free conditions. There were concentration-dependent decreases both in TC content and lipid-droplet-containing cell proportions when treated with TP from 40 ng.L-1 to 40 mg.L-1. The number of lipid droplets was also decreased in TP treated mesangial cells. CONCLUSION: TP has an inhibitive effect on OX-LDL intake in cultured rat mesangial cells, which is in a concentration-dependent manner from 40 ng.L-1 to 40 mg.L-1.

Animals↗
PubMed2003

[Synthesis of prodrugs of tacrine hydrochloride and evaluation of the stability and biodistribution in mice].

AIM: To synthesize acylated prodrug of tacrine hydrochloride (THA) to improve the infiltration ability across the blood brain barrier (BBB). METHODS: A series of prodrugs were prepared by acylation of the 7-amino group of THA. The degradation of prodrugs was investigated under different conditions. Biodistribution studies of N-butyramide-THA (BTHA) in mice were carried out to evaluate the function of brain targeting. RESULTS: The structures of prodrugs were confirmed by IR, 1HNMR and MS. All prodrugs were stable in different medium. Octanol-water partition coefficients indicated increased lipophlicity for various prodrugs compared to the THA. In vivo distribution studies showed that BTHA was mainly distributed in brain, blood and liver (the maximum concentrations were 17.5725, 13.1400 and 22.8279 mg.L-1, respectively), while the THA concentration were very low in lung and heart (the maximum concentrations were 4.9475 and 4.4925 mg.L-1, respectively). The BTHA concentration (2.4159 mg.L-1) was relatively high even 12 h after administration, showing that BTHA degraded more slowly in brain than in other tissues. CONCLUSION: The infiltration ability of THA across BBB was increased in the form of N-acylate-THA prodrug, indicating that this kind of prodrug is a promising brain-targeting delivery system.

Animals↗
PubMed2002

[Effect of local mild hypothermia on treatment of acute intracerebral hemorrhage, a clinical study].

OBJECTIVE: To observe the effect of local mild hypothermia on treatment of acute intracerebral hemorrhage. METHODS: Forty patients with acute intracerebral hemorrhage were matched according to age and state of illness at a ratio of one to one and then randomly divided into two groups of 20 patients: routine group (dehydrant, antihypertensive agent, etc were given) and hypothermia group (in addition to the general treatment, controllable semiconductor brain-protecting freezer was used to produce local hyperthermia at temperature of 6 degrees C for 48 hours). Immediately after admission and one week and 2 weeks after treatment cranium CT was conducted and the volume of cerebral edema was calculated by Tada's formula. RESULTS: There was no significant difference in the volume of edema and scores according to European Stroke Scale between the two groups at admission (P > 0.05). The volumes of edema one week and 2 weeks after therapy were 17.4 +/- 6.2 and 13.1 +/- 5.8 milliliter respectively in hypothermia group, both significantly lower than those in the routine group (33.8 +/- 16.0 and 22.4 +/- 12.2 milliliter respectively, P < 0.05). The scores according to European Stroke Scale one week and 2 weeks after therapy were 62.1 +/- 10.8 and 70.3 +/- 10.7 in hypothermia group, both significantly higher than those in the routine group (52.8 +/- 10.9 and 60.5 +/- 10.9 respectively, P < 0.05). No side effect caused by local hyperthermia was observed during the therapy. CONCLUSION: A safe and reliable treatment, local mild hypothermia combined with routine therapy is effective in protecting the brain of patients with intracerebral hemorrhage.

Adult↗
PubMed2002

Crystal structures of human GAR Tfase at low and high pH and with substrate beta-GAR.

Glycinamide ribonucleotide transformylase (GAR Tfase) is a key folate-dependent enzyme in the de novo purine biosynthesis pathway and, as such, has been the target for antitumor drug design. Here, we describe the crystal structures of the human GAR Tfase (purN) component of the human trifunctional protein (purD-purM-purN) at various pH values and in complex with its substrate. Human GAR Tfase exhibits pH-dependent enzyme activity with its maximum around pH 7.5-8. Comparison of unliganded human GAR Tfase structures at pH 4.2 and pH 8.5 reveals conformational differences in the substrate binding loop, which at pH 4.2 occupies the binding cleft and prohibits substrate binding, while at pH 8.5 is permissive for substrate binding. The crystal structure of GAR Tfase with its natural substrate, beta-glycinamide ribonucleotide (beta-GAR), at pH 8.5 confirms this conformational isomerism. Surprisingly, several important structural differences are found between human GAR Tfase and previously reported E. coli GAR Tfase structures, which have been used as the primary template for drug design studies. While the E. coli structure gave valuable insights into the active site and formyl transfer mechanism, differences in structure and inhibition between the bacterial and mammalian enzymes suggest that the human GAR Tfase structure is now the appropriate template for the design of anti-cancer agents.

Bacterial Proteins↗
PubMed2002

Initiation of O-glycan synthesis in IgA1 hinge region is determined by a single enzyme, UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase 2.

The hinge region of human immunoglobulin A1 (*IgA1) possesses multiple O-glycans, of which synthesis is initiated by the addition of GalNAc to serine or threonine through the activity of UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferases (pp-GalNAc-Ts). We found that six pp-GalNAc-Ts, pp-GalNAc-T1, -T2, -T3, -T4, -T6, and -T9, were expressed in B cells, IgA-bearing B cells, and NCI-H929 IgA myeloma cells. pp-GalNAc-T activities of these six enzymes for a synthetic IgA hinge peptide, which has nine possible O-glycosylation sites, were examined using a reversed phase-high performance liquid chromatography, a matrix-assisted laser desorption ionization time of flight mass spectrometry, and peptide sequencing analysis. pp-GalNAc-T2 showed the strongest activity transferring GalNAc to a maximum of eight positions. Other pp-GalNAc-Ts exhibited different substrate specificities from pp-GalNAc-T2; however, their activities were extremely weak. It was reported that the IgA1 hinge region possesses a maximum of five O-glycans, and their amino acid positions have been determined. We found that pp-GalNAc-T2 selectively transferred GalNAc residues to the same five positions. These results strongly suggested that pp-GalNAc-T2 is an essential enzyme for initiation of O-linked glycosylation of the IgA1 hinge region.

Amino Acid Sequence↗
PubMed2002

[Association of estrogen receptor gene polymorphism with cerebral infarction, a case-control study].

OBJECTIVE: To explore the association between estrogen receptor (ER) gene PvuII and XbaI polymorphisms and cerebral infarction among Chinese Han people. METHODS: Samples of peripheral blood white cell were extracted among 234 patients with cerebral infarction, aged 63.9 +/- 10.3, and 259 controls without cerebrovascular disease, aged 59.2 +/- 9.2, all of Chinese Han nationality. PCR-RFLP and genotyping of ER PvuII and XbaI polymorphisms were performed. Multiple Logistic regression analysis was made to explore the risk factors for cerebral infarction. RESULTS: After adjustment for major confounders including age, gender, smoking, alcohol drinking, education, history of hypertension, diabetes mellitus, coronary artery disease and hyperlipoidemia, multiple Logistic regression analysis showed that: (1) The Pp genotype of ER PvuII polymorphism increased the risk of cerebral infarction significantly (OR = 1.97, 95% CI: 1.21 - 3.21); (2) The ER XbaI polymorphism was not in association with cerebral infarction significantly; (3) The PPXx/Ppxx genotypes increased the risk of cerebral infarction significantly (OR = 1.67, 2.52 and 2.18 respectively, P < 0.05) before or after all subjects were stratified by the history of hypertension or hyperlipoidemia; and (4) The positive interaction between the ER PvuII polymorphism and the presence of hypertension or diabetes or hyperlipoidemia could increase the risk of cerebral infarction significantly. CONCLUSION: ER gene may be one of the genetic candidate genes for cerebral infarction among Chinese Han population.

Aged↗
PubMed2002

Characterization of a novel human UDP-GalNAc transferase, pp-GalNAc-T10.

A novel member of the human UDP-N-acetyl-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase (pp-GalNAc-T) gene family was cloned as a homolog of human pp-GalNAc-T7, and designated pp-GalNAc-T10. pp-GalNAc-T10 transcript was found in the small intestine, stomach, pancreas, ovary, thyroid gland and spleen. In a polypeptide GalNAc-transfer assay, recombinant pp-GalNAc-T10 transferred GalNAc onto a panel of mucin-derived peptide substrates. Furthermore, pp-GalNAc-T10 demonstrated strong transferase activity with glycopeptide substrates.

Amino Acid Sequence↗
PubMed2002

Cloning and characterization of a new human UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase, designated pp-GalNAc-T13, that is specifically expressed in neurons and synthesizes GalNAc alpha-serine/threonine antigen.

To date, 10 members of the UDP-N-acetyl-alpha-d-galactosamine:polypeptide N-acetylgalactosaminyltransferase (pp-GalNAc-T) family have been cloned and analyzed in human. In this study, we cloned and analyzed a novel human pp-GalNAc-T from an NT2 cell cDNA library, and we named it pp-GalNAc-T13. In amino acid sequences, pp-GalNAc-T13 was highly homologous, showing 84.3% identity, to pp-GalNAc-T1. Real time PCR analysis revealed pp-GalNAc-T13 to be highly and restrictively expressed in the brain and present at very low or undetectable levels in other tissues, in contrast to the ubiquitous expression of pp-GalNAc-T1. pp-GalNAc-T13 was abundantly expressed in all neuroblastoma cells examined and primary cultured neurons but not in glioblastoma cells and primary cultured astrocytes. pp-GalNAc-T13 exhibited much stronger activity to transfer GalNAc to mucin peptides, such as Muc5Ac and MUC7, than did pp-GalNAc-T1. In addition, pp-GalNAc-T13 differed in substrate specificity to pp-GalNAc-T1. pp-GalNAc-T13 was able to form a triplet Tn epitope, three consecutive GalNAc-Ser/Thr structures, on peptides encoded in syndecan-3, a proteoglycan expressed in neurons. pp-GalNAc-T13-deficient mice have been established in a previous work. Immunohistochemical study showed a remarkable decrease in Tn antigen expression in the cerebellum of the pp-GalNAc-T13 knockout mouse. pp-GalNAc-T13 would be a major enzyme responsible for the synthesis of O-glycan and specifically the Tn antigen epitope in neurons.

Amino Acid Sequence↗
PubMed2002

A novel GTP-binding protein hGBP3 interacts with NIK/HGK.

A novel human guanylate-binding protein (GBP) hGBP3 was identified and characterized. Similar as the two human guanylate-binding proteins hGBP1 and hGBP2, hGBP3 has the first two motifs of the three classical guanylate-binding motifs, GXXXXGKS (T) and DXXG, but lacks the N (T) KXD motif. Escherichia coli-expressed hGBP3 protein specifically binds to guanosine triphosphate (GTP). Using a yeast two-hybrid system, it was revealed that the N-terminal region of hGBP3 binds to the C-terminal regulatory domain of NIK/HGK, a member of the group I GCK (germinal center kinase) family. This interaction was confirmed by in vitro glutathione-S-transferase (GST) pull-down and co-immunoprecipitation assays.

Amino Acid Sequence↗