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Biomedical subjects

X W Wu

Publications and source records attributed to X W Wu.

18 recordsLinked to original sources
PubMed1998

Structure-based design and synthesis of small molecule protein-tyrosine phosphatase 1B inhibitors.

Protein-tyrosine phosphatase (PTP) inhibitors are attractive as potential signal transduction-directed therapeutics which may be useful in the treatment of a variety of diseases. We have previously reported the X-ray structure of 1,1-difluoro-1-(2-naphthalenyl)methyl] phosphonic acid (4) complexed with the human the protein-tyrosine phosphatase 1B (PTP1B) and its use in the design of an analogue which binds with higher affinity within the catalytic site (Burke, T. R., Jr. et al. Biochemistry 1996, 35, 15989). In the current study, new naphthyldifluoromethyl phosphonic acids were designed bearing acidic functionality intended to interact with the PTP1B Arg47, which is situated just outside the catalytic pocket. This residue has been shown previously to provide key interactions with acidic residues of phosphotyrosyl-containing peptide substrates. Consistent with trends predicted by molecular dynamics calculations, the new analogues bound with 7- to 14-fold higher affinity than the parent 4, in principal validating the design rationale.

Drug Design↗
PubMed1997

Binding properties and inhibition of platelet aggregation by a monoclonal antibody to CD31 (PECAM-1).

CD31/platelet endothelial cell adhesion molecule 1 (PECAM-1) is expressed on platelets, endothelial cells, myeloid cells, monocytes, and certain lymphocyte subsets. It has been shown that CD31 is involved in the homophilic and heterophilic cellular adhesion and leukocyte transendothelial migration, but little is known about the role of CD31 in platelet functions. Previously we have shown that monoclonal antibody (MAb) AAP2 produced in our laboratory bound to a 110-kD platelet antigen and gave an enhanced binding to activated platelet membrane. In this study we demonstrated that platelet lysate depleted of the antigen through adsorption by an AAP2-solidified affinity column was bound by MAbs against CD62 and CD42 but not by MAb 5.6E against CD31 or AAP2 on the immunoblot. Rabbit antibodies against CD31 completely inhibited the binding of AAP2 to platelets in the flow cytometry analysis. This indicates that AAP2 is specifically against CD31. 125I-labeled AAP2 bound to resting platelets with 5587 +/- 1765 sites/platelet and a Kd of 1 nmol/L and to thrombin-activated platelets with 17,625 +/- 4865 sites/platelet and a Kd of 0.24 nmol/L. Addition of 10 micrograms/mL AAP2 inhibited the aggregation induced by 4 mumol/L ADP by 78.6%, 6 mumol/L epinephrine by 79.4%, 1 microgram/mL collagen by 78.7%, and 0.25 U/mL thrombin by 29%. The platelet aggregation was completely restored when higher concentration of agonists were used. MAb 5.6E did not have any effect on platelet aggregation. These results suggest that AAP2 binds to a special epitope of CD31 on platelets and that CD31 is involved in platelet aggregation.

Adenosine Diphosphate↗
PubMed1996

Molecular dynamics simulations of synthetic peptide folding.

Because the time scale of protein folding is much greater than that of the widely used simulations of native structures, a detailed report of molecular dynamics simulations of folding has not been available. In this study, we included the average solvent effect in the potential functions to simplify the calculation of the solvent effect and carried out long molecular dynamics simulations of the alanine-based synthetic peptides at 274 K. From either an extended or a randomly generated conformation, the simulations approached a helix-coil equilibrium in about 3 ns. The multiple minima problem did not prevent helix folding. The calculated helical ratio of Ac-AAQ-AAAAQAAAAQAAY-NH2 was 47%, in good agreement with the circular dichroism measurement (about 50%). A helical segment with frayed ends was the most stable conformation, but the hydrophobic interaction favored the compact, distorted helix-turn-helix conformations. The transition between the two types of conformations occurred in a much larger time scale than helix propagation. The transient hydrogen bonds between the glutamine side chain and the backbone carbonyl group could reduce the free energy barrier of helix folding and unfolding. The substitution of a single alanine residue in the middle of the peptide with valine or glycine decreased the average helical ratio significantly, in agreement with experimental observations.

Alanine↗
PubMed1996

A monoclonal antibody that recognizes a 110-kDa protein primarily located on the platelet alpha-granule, which is translocated to and upgraded on the surface membrane of platelets upon activation.

A murine monoclonal antibody, designated as MAb AAP2, was produced by immunizing human activated platelets to BALB/c mice. MAb AAP2 recognizes a platelet membrane antigen that was present in trace amount on the membrane of resting platelets, and was strongly expressed on the membrane after activation with thrombin as demonstrated by immunofluorescence microscopy. Platelet granule fractionation by ultracentrifugation on sucrose density gradient and metrizamide showed that the target antigen of MAb AAP2 was located in alpha-granules but not in lysosomes or dense granules. On Western blot prepared with whole platelet lysate, MAb AAP2 bound to a 110-kDa protein under nonreducing and reducing conditions. These results suggest that MAb AAP2 recognizes a 110-kDa platelet antigen, which is primarily located on the alpha granule of platelets and translocated to and upgraded on the surface membrane upon activation.

Animals↗
PubMed1996

Purification and characterization of lupus anticoagulant like protein from Agkistrodon halys brevicaudus venom.

By means of CM-Sephadex C-25, DEAE-Sephadex A-50, Sephadex G-200, and Sephadex G-75 chromatographies, a lupus anticoagulant like protein (LALP) from Agkistrodon halys brevicaudus was purified. On SDS-PAGE, the purified LALP had a molecular weight of 25,500 daltons under non-reducing condition and 15,000 daltons under reducing condition. The isoelectric point was pH 5.6. Its N terminal amino acid sequencing revealed a mixture of 2 sequences: DCP(P/S)(D/G)WSSYEGH(C/R)(Q/K). It was devoid of phospholipase A, fibrino(geno)lytic, 5'-nucleotidase, L-amino acid oxidase, phosphomonoesterase, phosphodiesterase and thrombin-like activities, which were found in crude venom. In the presence of LALP, PT, aPTT, and dRVVT of human plasma were markedly prolonged and its effects were concentration-dependent but time-independent. The inhibitory effect of LALP on the plasma clotting time was enhanced by decreasing phospholipid concentration in TTI test. The individual clotting factor activity was not affected by LALP when higher dilutions of LALP-plasma mixture were used for assay. Russell's viper venom time was shortened when high phospholipid confirmatory reagent was used. Therefore, the protein has lupus anticoagulant property.

Agkistrodon↗
PubMed1996

[Study on treatment of retinitis pigmentosa with traditional Chinese medicine by Flicker electroretinogram].

Study on treatment of 54 patients (106 eyes) of retinitis pigmentosa (RP) with traditional Chinese medicine was conducted by using modified method of electroretinography. Results showed: (1) Flicker response of electroretinogram was the most sensitive-criterion in examination, it was more effective when combined with infrared spectrogram. (2) The 30 Hz flicker index, response time were improved after TCM therapy in different hereditary types of RP, the improvement was significant in patients with Yang-Deficiency of Spleen-Kidney Syndrome and those of autosomal dominant inheritance type (P < 0.01). (3) Decrease of phase angle (phi) under different frequency of flicker after treatment was also significant statistically. The results suggested that flicker responses, which represents mainly retinal cone activity of patients, could be improved to a certain extent by TCM treatment, even in those with advanced retinal degeneration. TCM treatment could also enhance the bioactivity of nerve network and therefore have a definite significance in retarding the progression of disease and keeping the central vision. The flicker ERG, especially its flicker index, is an effective, sensitive and useful parameter for detection of visual function in patient with retinitis pigmentosa.

Adolescent↗
PubMed1994

[Transcervical salpingography and tubal recanalization].

The results of transcervical salpingography and tubal recanalization by means of modified Thurmond and Rösch's technique were reported. Proximal tubal obstruction was diagnosed in 20 infertile women by X-ray hysterosalpingography and/or laparoscopy. Our results showed that tubal recanalization was achieved in 19(95%) of 20 patients, four patients became pregnanCy following the procedure. Distal tubal diseases were seen in 8 of 20 patients. Follow up studies revealed tubal patency was maintained in 7(54%) of 13 patients. The mean radiation dosage received by the patient was 6.35mGy. Compared with Thurmond and Rösch technique the modified technique has the advantage of decreasing the time of fluoroscopy and is a safe, effective and simple method for the diagnosis and treatment of infertile women with proximal tubal obstruction.

Adult↗
PubMed1993

Mechanism of platelet aggregation induced by a monoclonal antibody requiring Fc portion.

A monoclonal antibody designated Apt4, which is IgG1, was produced by fusion of mouse myeloma cells to spleen cells from a BALB/c mouse immunized with normal human platelets. Apt4 whole IgG caused the aggregation of both platelet rich plasma (PRP) and washed platelets from normal subjects and a patient with Bernard Soulier syndrome but not those from two patients with the Type 1 Glanzmann's thrombasthenia. No aggregation was observed when Apt4 F(ab')2 fragments were used. Immunofluorescence study showed that both whole IgG and F(ab')2 fragments of Apt4 bound to fresh or formalin fixed platelets from normal subjects and a patient with Bernard Soulier syndrome but not to those from two patients with Glanzmann's thrombasthenia. Aggregation induced by Apt4 IgG was inhibited by EDTA (10 mM), PGE1 (1 mM), 2-deoxy-D-glucose/antimycin (1.4 uM), and apyrase (20 units/ml). Preincubation of normal PRP with monoclonal anti-GPIIb/IIIa or anti-GPIb antibodies completely or partially inhibited the Apt4-induced aggregation, whereas anti-GPIIIa antibodies have no effects on this activation. Monoclonal ant-Fc gamma RII antibody (IV.3) inhibited Apt4 induced aggregation. Immunoprecipitation of 125I-labeled platelet membrane lysate by Apt4 IgG showed two protein bands with a molecular weight of 145,000 and 95,000 daltons respectively under non-reducing condition, which are corresponding to GPIIb and GPIIIa. In conclusion, Apt4 antibody binds to GPIIb/IIIa complex and induces aggregation, requiring energy metabolism, calcium, ADP release and Fc portion of IgG to interact with Fc receptor, but independent of thromboxane A2 formation.

Animals↗
PubMed1992

Two independent mutational events in the loss of urate oxidase during hominoid evolution.

Urate oxidase was lost in hominoids during primate evolution. The mechanism and biological reason for this loss remain unknown. In an attempt to address these questions, we analyzed the sequence of urate oxidase genes from four species of hominoids: human (Homo sapiens), chimpanzee (Pan troglodytes), orangutan (Pongo pygmaeus), and gibbon (Hylobates). Two nonsense mutations at codon positions 33 and 187 and an aberrant splice site were found in the human gene. These three deleterious mutations were also identified in the chimpanzee. The nonsense mutation at codon 33 was observed in the orangutan urate oxidase gene. None of the three mutations was present in the gibbon; in contrast, a 13-bp deletion was identified that disrupted the gibbon urate oxidase reading frame. These results suggest that the loss of urate oxidase during the evolution of hominoids could be caused by two independent events after the divergence of the gibbon lineage; the nonsense mutation at codon position 33 resulted in the loss of urate oxidase activity in the human, chimpanzee, and orangutan, whereas the 13-bp deletion was responsible for the urate oxidase deficiency in the gibbon. Because the disruption of a functional gene by independent events in two different evolutionary lineages is unlikely to occur on a chance basis, our data favor the hypothesis that the loss of urate oxidase may have evolutionary advantages.

Amino Acid Sequence↗
PubMed1990

Genetic polymorphism of MHC class III and GLO in Chinese Yao nationality.

Yao nationality is one of the minority nationalities living mainly in South China (Guangxi Province). The purpose of this study was to provide data of MHC class III and GLO in Chinese Yao nationality and the different genetic background of Yao and Han nationality, the latter representing the major nationality in China. The genetic polymorphism of MHC class III and GLO in Chinese Yao nationality was determined. Previously the Japanese were considered to have the lowest C2*C frequencies (0.9386), but now we ascertained that the Yao have the lowest C2*C frequencies (0.9336). The data concerning gene frequencies of Yao are presented. They were also compared with the available data of Han.

China↗
PubMed1990

Genetic polymorphisms of HLA class III and GLO1 in Chinese Yao nationality.

Yao is one of the minority nationalities located mainly in the South of China (Guang Xi province). The purpose of this study was to examine HLA class III and GLO1 in Yao nationality to identify the difference between Yao and Han. Han is the major nationality in China. Yao has the lowest C2*C frequency (0.9336) in the world. Before this study the lowest C2*C frequency known was that of the Japanese (0.9386). Gene frequencies in Yao are the following: C2*C = 0.9336, C2*B = 0.0664; BF*S = 0.9071, BF*F = 0.0929; C4A*4 = 0.0253, C4A*3 = 0.6061, C4A*2 = 0.2121, C4A*1 = 0.0152, C4A*Q0 = 0.1414; C4B*3 = 0.0051, C4B*2 = 0.0657, C4B*1 = 0.7071, C4B*92 = 0.0455, C4B*95 = 0.0253, C4B*96 = 0.0253, C4B*12 = 0.0051, C4B*Q0 = 0.1212; GLO1*1 = 0.1161, GLO1*2 = 0.8839. We have compared these data with those reported for Han.

Blood Donors↗
PubMed1989

Urate oxidase: primary structure and evolutionary implications.

Urate oxidase, or uricase (EC 1.7.3.3), is a peroxisomal enzyme that catalyzes the oxidation of uric acid to allantoin in most mammals. In humans and certain other primates, however, the enzyme has been lost by some unknown mechanism. To identify the molecular basis for this loss, urate oxidase cDNA clones were isolated from pig, mouse, and baboon, and their DNA sequences were determined. The mouse urate oxidase open reading frame encodes a 303-amino acid polypeptide, while the pig and baboon urate oxidase cDNAs encode a 304-amino acid polypeptide due to a single codon deletion/insertion event. The authenticity of this single additional codon was confirmed by sequencing the mouse and pig genomic copies of the gene. The urate oxidase sequence contains a domain similar to the type 2 copper binding motif found in other copper binding proteins, suggesting that the copper ion in urate oxidase is coordinated as a type 2 structure. Based upon a comparison of the NH2-terminal peptide and deduced sequences, we propose that the maturation of pig urate oxidase involves the posttranslational cleavage of a six-amino acid peptide. Two nonsense mutations were found in the human urate oxidase gene, which confirms, at the molecular level, that the urate oxidase gene in humans is nonfunctional. The sequence comparisons favor the hypothesis that the loss of urate oxidase in humans is due to a sudden mutational event rather than a progressive mutational process.

Amino Acid Sequence↗
PubMed1989

[Production and application of anti-human platelet GP IIb/IIIa monoclonal antibodies].

Four types of anti-human platelet glycoprotein IIb/IIIa (GP IIb/IIIa)monoclonal antibodies (McAb), termed HIP2, HIP4, HIP7, HIP8, were obtained in our laboratory. All of them recognized GP IIb/IIIa complex except that HIP2 recognized GP IIb. As to the effect of the four McAbs on platelet aggregation, the results showed: 1) HIP4 and HIP8 can completely inhibit platelet aggregation induced by ADP or collagen, but not that induced by thrombin or ristocetin. 2) HIP2 was able to activate platelet aggregation directly. But it is Ca++ and complement dependent; 3) HIP7 did not show any effect on platelet aggregation induced by collagen, ADP, thrombin or ristocetin. When clinically studied, some cases of platelet-associated diseases such as thrombocytasthenia and thrombocytopenia had abnormal responses to the above McAbs. In addition, we also found that these McAbs can stimulate hematopoiesis in CFU-E assay.

Animals↗
PubMed1988

Generation of cDNA probes directed by amino acid sequence: cloning of urate oxidase.

Urate oxidase (E.C. 1.7.3.3) catalyzes the oxidation of uric acid to allantoin in most mammals except humans and certain primates. The amino-terminal amino acid sequence for porcine urate oxidase was determined and used in a novel procedure for generating complementary DNA (cDNA) probes to this amino acid sequence. The procedure is based on the polymerase chain reaction and utilizes mixed oligonucleotide primers complementary to the reverse translation products of an amino acid sequence. This rapid and simple cDNA cloning procedure is generally applicable and requires only a partial amino acid sequence. A cDNA probe developed by this procedure was used to isolate a full-length porcine urate oxidase cDNA and to demonstrate the presence of homologous genomic sequences in humans.

Amino Acid Sequence↗