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W Y Yu

Publications and source records attributed to W Y Yu.

At least 19 recordsLinked to original sources
PubMed1992

Identification of residues involved in polymorphic antibody binding epitopes on HLA-DR molecules.

Based on previous studies it was predicted that amino acids 4 or 25 of the DR4 beta 1 and DR7 beta 1 chains are involved in polymorphic antibody binding epitopes on DR4 or DR7 molecules. These predictions were tested by analyzing monoclonal antibody (mAb) binding to transfectants expressing mutant DR4 beta 1 or DR7 beta 1 chains with single amino acid substitutions at positions 4 or 25. Antibody binding to transfectants expressing additional DR4/7 beta 1 hybrids was also analyzed to assess further the contributions of four segments of the DR4 beta 1 or DR7 beta 1 chains: amino acids 1-20, 21-40, 41-97, and the beta 2 domain. Single amino acid substitutions at positions 4 and 25 of the DR4 beta 1 chain or DR7 beta 1 chain eliminate binding of several mAb to DR4 or DR7 molecules, documenting that these residues are involved in antibody epitopes. However, the data with the hybrid DR4/7 beta 1 chains indicate that some of these epitopes require contributions from both segments 1-20 and 21-40 of these DR beta chains, whereas other epitopes can be generated by placing the appropriate segment in the context of the other DR beta chain. In addition, the data with other mAb indicate that their epitopes are determined primarily by sequences within the 41-97 segment or in the beta 2 domain.

Amino Acids↗
PubMed1992

Diverse locations of amino acids in HLA-DR beta chains involved in polymorphic antibody binding epitopes on DR(alpha, beta 1*0101), DR(alpha, beta 1*1101), and DR(alpha,beta 3*0202) molecules.

In a previous study, we used transfectants expressing hybrid HLA-DR(beta 1*0403)/DR(beta 1*0701) chains to map sequences involved in polymorphic antibody binding epitopes on DR(alpha, beta 1*0403) or DR(alpha, beta 1*0701) molecules. Amino acids 1-40 of the beta 1 domain were found to make the major contributions to most of the antibody binding epitopes studied. To begin to localize sequences that contribute to polymorphic antibody epitopes on DR(alpha,beta 1*0101), DR(alpha,beta 1*1101) and DR(alpha,beta 3*0202) molecules, we used indirect immunofluorescence and flow cytometry to assess the binding of mAb to transfectants expressing hybrid DR(beta 1*0101)/DR(beta 1*1101) or DR(beta 1*1101)/DR(beta 3*0202) chains that divide the DR beta chain into three segments: amino acids 1-40, 41-97, and the beta 2 domain. The results indicate that amino acids 41-97 of the beta 1 domain on DR(beta 1*0101), DR(beta 1*1101), or DR(beta 3*0202) are critical in most of the epitopes, including those recognized by human antibodies MP4 and MP12, and mouse mAb GS88.2, I-LR1, 21r5, and 7.3.19.1, whereas amino acids 1-40 of DR(beta 1*1101) are critical in the epitope recognized by the MCS-7 mAb, and both segments 1-40 and 41-97 of DR(beta 1*1101) are important in the epitopes recognized by the I-LR2 and UL-52 mAbs. Based on these data and comparison of DR beta allelic protein sequences, the residues that may play critical roles in these antibody binding epitopes are predicted.

Amino Acids↗
PubMed1991

Antigen-specific T cells with monogamous or promiscuous restriction patterns are sensitive to different HLA-DR beta chain substitutions.

The contributions of the amino acids at 13 polymorphic positions in the HLA-DR7 beta 1 chain to T cell recognition of two antigenic peptides of tetanus toxin (p2 and p30) were assessed using transfectants expressing mutant DR7 beta 1 chains as APC for six toxin-specific T cell clones with two different restriction patterns: monogamous (restricted by DR7 only) or promiscuous (restricted by DR7; DR1; DR2, Dw21; and DR4, Dw4). Each of the 13 substitutions significantly decreased or eliminated the ability of the DR7 molecule to present a peptide to one or more of the T cell clones, but none of the substitutions abolished recognition by all clones. Interestingly, substitutions at positions 4 and 25, which are predicted in the class II model to be located outside the peptide binding groove, decreased the ability of the DR7 molecule to present Ag to some clones but not to others. Each of the four clones specific for the p2 peptide and the two clones specific for peptide p30 had a different reactivity pattern to the panel of DR7 beta 1 mutants, indicating that the TCR of each clone has a different view of the p2/DR7 or p30/DR7 complex. These data emphasize the complexity of the interactions of multiple residues in DR7 beta 1 chains in Ag-specific T cell recognition.

Amino Acid Sequence↗
PubMed1991

Polymorphic HLA-DR7 beta 1 chain residues that are involved in T cell allorecognition.

The contributions to allorecognition of polymorphic amino acids in the HLA-DR7 beta 1 chain were analyzed by using mutant DR7 beta 1 chains with single amino acid substitutions at position 4, 11, 13, 25, 30, 37, 57, 60, 67, 70, 71, 74, or 78. Transfectants expressing mutant DR7 molecules were used as stimulators for six DR7-alloreactive T cell clones. The majority of the substitutions had profound effects on the ability of the DR7 molecule to stimulate one or more T cell clones. Nine of the 13 substitutions completely abrogated recognition by at least one clone. The finding that each of the substitutions in the beta-strands in the floor of the peptide binding groove affected T cell allorecognition supports the model of allorecognition in which the complex of a self-peptide bound to a class II molecule is recognized by the TCR. Interestingly, the substitution at position 4, which is predicted to be located outside the peptide binding groove, decreased the ability of the DR7 molecule to stimulate some clones. Each of the DR7-alloreactive T cell clones had a unique reactivity pattern in response to the different mutant molecules, indicating that the TCR of each clone recognized the DR7 molecule differently. Surprisingly, many of the mutant DR7 molecules induced proliferation by one or more clones that was greater than 125% of the proliferation induced by the wild-type DR7 molecule. These data indicate that multiple polymorphic residues, predicted in the class II model to be located in both the beta-strands and alpha-helix of the DR7 beta 1 chain, contribute to allorecognition of the DR7 molecule.

Amino Acid Sequence↗
PubMed1991

Single amino acid changes in DR and antigen define residues critical for peptide-MHC binding and T cell recognition.

Single amino acid substitutions of Ag and MHC were used to analyze the fine structure of the influenza hemagglutinin (HA)-derived epitope (HA 307-319) recognized in the context of DR7 molecules by a T cell clone. Putative T cell (HA 308, 310, 311, 313, and 316) and DR (HA 309, 312, and 317) contact residues of the Ag were identified by the use of single amino acid-substituted analogs that were tested for their T cell-activating and DR-binding capacities. The peptide-DR7-T cell interaction was further characterized by the use of a panel of 13 site-directed DR7 mutant transfectants analyzed for their capacity to present Ag to T cells, and for their purified mutant DR7 molecules to bind HA 307-319 or its single amino acid-substituted analogs. Eight mutants lost their Ag-presenting function, whereas only one had any decrease in peptide binding. Finally, for three of the mutants it was possible to correct the deleterious effects of mutation by using a particular single amino acid-substituted analog of the peptide molecule. The observed pattern of complementation led to a model that predicts that the Ag assumes an extended conformation, with a turn, in the binding groove, such that the following residues are in close proximity: DR 86-HA 309, DR 71-HA 312, DR 30-HA 314, and 315.

Amino Acid Sequence↗
PubMed1991

DRw11 haplotypes: continuum of DRB1 diversity augmented by unique DQ/DRw52 associations.

cDNA sequencing of the first domains of DRB1, DRB3, DQA1, and DQB1 alleles was used to examine the extent of diversity in American black individuals expressing several DRw11 haplotypes. In addition to previously described DRw11 alleles, DRB1*1102 and DRB1*1103, two new DRB1 alleles, DRB1*11012 and DRB1*11042, were identified which differ from previously described alleles at the nucleic acid but not at the protein level. Gene conversion-like events have likely generated the DRw11 microvariation resulting in the merging of DRw11 with the DRw13 allele family. The DRw11 alleles are associated with various DQ alleles: DQw1 (DQw5 and DQw6), DQw7, and a serologically undefined DQ allele. This undefined DQ molecule, comprised of a DQ alpha/beta combination encoded by a DQw7 alpha gene (DQA1*0301) and a DQw2 beta gene (DQB1*0201), was previously observed in some DR7 and DR9 haplotypes. DRw11 haplotype diversity is augmented by the association of one of the DRw11 alleles with the DRw52c allele in contrast to the more common DRw11, DRw52b association. The extensive diversity exhibited by the DRw11 and DRw13 family of haplotypes coupled with their high frequency in populations of African ancestry suggest that the DRw11/w13 allele family may be very old and/or that these haplotypes carry some selective advantage.

Amino Acid Sequence↗
PubMed1991

Expression of pro-urokinase cDNA in Chinese hamster ovary cell line.

Expression vectors containing the pro-urokinase (pro-UK) cDNA (pSV2-proUK) and a dihydrofolate reductase cDNA (pSV2-dhfr or MMTV-dhfr) were cotransfected into CHO-dhfr- cells by the calcium phosphate precipitation technique. The dhfr+ transformants were selected by fibrinolytic agarose plate assay. Two colonies, named CLF-14 and CLF-8, exhibited significantly high expression levels of the biological activity of urokinase-type plasminogen activator (mu-Pa). They reached more than 24 IU/10(6) cells/48 h and 16 IU/10(6) cells/48 h, respectively. Examination of the cell supernatants for mu-Pa antigenicity using ELISA method also showed strong positive results, and the quantities of expression were about 0.14-0.22 micrograms/10(6) cells/48 h and 0.08-0.14 micrograms/10(6) cells/48 h, respectively. The mu-Pa secreted by stable transformed cells could be completely inhibited by UK anti-serum, but not by tissue-type plasminogen activator (t-PA) antiserum nor by normal rabbit serum.

Animals↗
PubMed1991

Percutaneous suction aspiration for osteomyelitis. Report of two cases.

The nucleotome, a recently developed instrument for percutaneous disc excision, was used for suction aspiration in two cases of osteomyelitis of the spine. The technique obtained significant amounts of pus, serosanguinous material, and tissue, which provided adequate samples for histologic examination and culture. Both patients obtained immediate relief of pain after a significant amount of pus and infected material was removed. Appropriate antibiotics were used for subsequent control of the infections. The risk and morbidity of this technique are no greater than with conventional needle biopsy.

Adult↗
PubMed1990

Identification of amino acids in HLA-DPw4b beta and -DR5 beta 1 chains that are involved in antibody binding epitopes using site-directed mutagenesis and DNA-mediated gene transfer.

Based on comparisons of the amino acid sequences of the beta chains of HLA class II molecules that do or do not bind the I-LR1 monoclonal antibody, we predicted that glutamic acid 56 of I-LR1-positive DPw2, DPw3, and DPw4b beta chains and the analogous glutamic acid 58 of I-LR1-positive DR5 beta 1 chains are involved in the I-LR1 epitope. Site-directed mutagenesis of DPw4b beta and DR5 beta 1 cDNAs was used to change the codons for glutamic acid 56 in DPw4b beta and glutamic acid 58 in DR5 beta 1 to the codon for alanine found in I-LR1-negative beta chains. Transfectants expressing wild-type DPw4b beta chains or DR5 beta 1 chains bind the I-LR1 monoclonal antibody, whereas transfectants expressing the mutant DPw4b beta or DR5 beta 1 chains do not bind I-LR1. Therefore, DPw4b beta glutamic acid 56 and DR5 beta 1 glutamic acid 58 are involved in the epitope recognized by the I-LR1 monoclonal antibody. Interestingly, the DR5 beta 1 glutamic acid----alanine 58 substitution also causes the loss of binding of two DR5-specific monoclonal antibodies to DR5 beta 1 molecules. Because the sequences of amino acids 36 to 64 of the DPw4b beta chain and 38 to 66 of the DR5 beta 1 chain are identical, these data raise some interesting issues about the formation of antibody epitopes on class II molecules.

Amino Acid Sequence↗
PubMed1989

Seat belt injuries of the lumbar spine--stable or unstable?

Twenty six patients with seat belt injuries of the lumbar spine were admitted into the Spinal Cord Injury Unit of the University Hospital, University of British Columbia, in the past 10 years. Four patients with pure ligamentous injuries were primarily treated surgically. Sixteen patients were treated with closed methods with a Stryker frame followed by a body cast or brace. Significant angulation with spinal deformity occurred in 6 patients. The common factor of failure of closed treatment was the inadequate reduction of initial angulation. When the initial angulation at the fracture site was adequately reduced, closed methods were associated with satisfactory results with no serious disability seen in long term follow-up. Open reduction with fixation with compression rods or wiring and fusion invariably leads to good results. It is recommended that patients with seat belt fractures of the lumbar spine may be treated by a closed method provided good reduction is obtained initially, otherwise open reduction and posterior fusion is more preferable.

Accidents, Traffic↗
PubMed1989

[Prevention of mercury vapor contamination resulting from scraps of silver amalgam and the remainder of mercury].

Silver amalgam is applied in large amount in clinical practice, which will result in mercury vapour contamination of the stomatological environment. It is important to dispose properly of the scraps of silver amalgam and the remaining mercury, in order to reduce mercury vapour. This experiment shows that X-ray fixer solution is apparently more effective than water in preventing the escape of mercury vapour. Furthermore, such solution is available in hospitals and the used solution can also be utilized. The proper storage of silver amalgam scraps and the remaining mercury in X-ray fixer solution is apparently more effective than water in preventing the escape of mercury vapour. Furthermore, such solution is available in hospitals and the used solution can also be utilized. The proper storage of silver amalgam scraps and the remaining mercury in X-ray fixer solution will help to reduce the level of mercury vapour contamination of the stomatological environment.

Dental Amalgam↗
PubMed1988

Analysis of the molecular specificities of anti-class II monoclonal antibodies by using L cell transfectants expressing HLA class II molecules.

Expressible HLA class II alpha- and beta-chain cDNA were used for DNA-mediated gene transfer to produce L cell transfectants expressing single types of human class II molecules. Cloned transfectants expressing nine different class II molecules were isolated: DR alpha: DR1 beta I, DR alpha: DR4 beta I, DR alpha: DR5 beta I, DR alpha: DR5 beta III (DRw52), DR alpha: DR7 beta I, DR alpha: DR4/7 beta IV (DRw53), DQ7 alpha: DQw2 beta, DQ7 alpha: DQw3 beta, and DPw4 alpha: DPw4 beta. These class II-expressing transfectants were used to analyze by flow cytometry the molecular specificities of 20 anti-class II mAb. These analyes indicate that some mAb are more broadly reactive than was previously thought based on immunochemical studies. In contrast, the narrow molecular specificities of other anti-class II mAb were confirmed by this approach. Transfectants expressing human class II molecules should be valuable reagents for studies of B cell and T cell defined epitopes on these molecules.

Animals↗
PubMed1988

A newly characterized HLA-DP beta-chain allele. Evidence for DP beta heterogeneity within the DPw4 specificity.

cDNA clones corresponding to the DPw4 alpha- and DPw4 beta-chains were isolated from a cDNA library prepared from a DPw4 homozygous cell line, their nucleotide sequences were determined, and the corresponding amino acid sequences were deduced. This DPw4 alpha-chain is identical to the conserved DP alpha-chains from DPw4 and DPw2 haplotypes, although the DPw4 beta-chain (referred to as DPw4b beta) differs from all reported DP beta-chain sequences. The DPw4b beta-chain differs from the reported DPw4 beta sequence (referred to as DPw4a beta) at three amino acid positions in the first domain (36, 55, and 56). The DPw4b beta-chain sequence differs from the DPw2 beta-chain sequence only at position 69 in the first domain, suggesting that the lysine at position 69 in DPw4b beta and the glutamic acid at position 69 in DPw2 beta contribute to the epitopes that define "DPw4-ness" and "DPw2-ness," respectively. In addition, the patterns of sequence identities and differences among the DPw4b beta-, DPw4a beta-, DPw2 beta-, and DPw3 beta-chains suggest that the DPw4b beta sequence arose via a gene conversion event or a point mutation. The I-LR1 mAb, which was previously found to bind only to DPw2, DPw3, and DR5 molecules, binds to an L cell transfectant expressing the DPw4 alpha:DPw4b beta molecule. The DPw4b beta sequence provides the first evidence for structural heterogeneity within the DPw4 specificity.

Amino Acid Sequence↗
PubMed1987

Isolated colonic tuberculosis.

Two cases of isolated colonic tuberculosis are reported, and recent literature on this field is reviewed. Isolated colonic tuberculosis is defined as a tuberculosis which exists in the colon except for ileocaecum, without focus in any other organ. The morphological changes are tuberculous granulation primarily located to the submucosa layer of the colon with smooth surfaces of both mucous and serous membrane. Its clinical features are atypical, just like those on X-ray examination, and even on frozen biopsy, it may sometimes be misdiagnosed. The treatment of choice is resecting the diseased segment of colon combined with anti-tuberculosis therapy.

Adult↗
PubMed1986

Correlation between auditory reaction time and intelligence.

Discriminative reaction times to auditory stimuli were measured for 150 students of the local Chinese population. Pearson's correlation with scores on the Standard Progressive Matrices and RTs was negative, becoming -0.30 when slower trials were eliminated. The possible basis for improvement was discussed in relation to cognitive processes and the general theory of assessing intelligence.

Adolescent↗
PubMed1985

Closed reduction of lumbosacral fracture dislocations.

A unique method for closed reduction of lumbosacral fracture dislocations that uses a circle-electric bed is described. Fine radiological description of the injury with computed tomography scanning allows the application of appropriate forces to facilitate the reduction, while having the patient awake during the procedure greatly reduces the chance of introducing further neurological deficit.

Adult↗