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Biomedical subjects

W Y Yu

Publications and source records attributed to W Y Yu.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1985

Colonic variceal bleeding in a child.

A 5-year-old girl with biliary atresia is described who developed lower gastrointestinal bleeding from colonic varices. Vasopressin infusions temporarily controlled the bleeding. Following a right hemicolectomy the bleeding has not recurred.

Child, Preschool↗
PubMed1984

Detection of interaural time differences for clicks and tone pips: effects of interaural signal disparity.

The ability to detect small interaural time differences (delta t) was determined in 4 subjects using clicks or long tone pips of various interaural signal disparities which are expressed as the extent of interaural spectral overlaps. The interaural signal disparity was varied by changing (a) the interaural pulse duration difference (delta d) for clicks, or (b) the interaural carrier frequency difference (delta f) for tone pips. In either case, the sensitivity to delta t was maximal under diotic presentations and declined with delta d or delta f. The overall sensitivity to delta t was remarkably higher for clicks than for long tone pips. The results indicate that both (a) the extent of binaural spectral overlaps and (b) the structure of acoustic stimuli are important in detecting small interaural time differences of binaural sounds.

Acoustic Stimulation↗
PubMed1975

Mechanicla properties and mineral content of avascular and revascularizing cortical bone.

The mechanical properties of avascular and revascularizing bone and their mineral content were studied in thirty adult dogs. The strength and mineral content of avascular bone decreased in the early phase of avascular necrosis, and with revascularization the bone-mineral content increased but the mechanical strength decreased further. In the normal bone the mechanical strength increased with an increase in mineral content.

Animals↗
PubMedDate not supplied

Characterization of structure and diffusion behaviour of Ca-alginate beads prepared with external or internal calcium sources.

Ca-alginate beads were prepared with either external or internal calcium sources. The structures of both beads were investigated with the aid of scanning electron microscopy (SEM) and confocal microscopy. It was shown that the beads with internal calcium source had a looser structure and bigger pore size than those with external calcium source. The attempts to interpret the difference were carried out by determining the Ca content within the beads at various times, which indicated that it was the different gelation mechanisms that caused the difference of structures of both beads. Furthermore, it was also found that the diffusion rate of haemoglobin (Hb) within the beads with an internal calcium source was faster than that of the beads with an external one, which was consistent with the observation of their structures.

Alginates↗