Biomedical subjects
Publications and source records attributed to D M Wong.
Allele frequencies for 15 STR loci, namely D8S1179, D21S11, D7S820, CSF1PO, D3S1358, TH01, D13S317, D16S539, D2S1338, D19S433, vWA, TPOX, D18S51, D5S818 and FGA, which are tested for by PE Applied Biosystem's Identifier kit, were obtained from a sample of 325 unrelated Chinese in Hong Kong.
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Kinetic and structural data are presented on the interaction with Torpedo californica acetylcholinesterase (TcAChE) of (+)-huperzine A, a synthetic enantiomer of the anti-Alzheimer drug, (-)-huperzine A, and of its natural homologue (-)-huperzine B. (+)-Huperzine A and (-)-huperzine B bind to the enzyme with dissociation constants of 4.30 and 0.33 microM, respectively, compared to 0.18 microM for (-)-huperzine A. The X-ray structures of the complexes of (+)-huperzine A and (-)-huperzine B with TcAChE were determined to 2.1 and 2.35 A resolution, respectively, and compared to the previously determined structure of the (-)-huperzine A complex. All three interact with the "anionic" subsite of the active site, primarily through pi-pi stacking and through van der Waals or C-H.pi interactions with Trp84 and Phe330. Since their alpha-pyridone moieties are responsible for their key interactions with the active site via hydrogen bonding, and possibly via C-H.pi interactions, all three maintain similar positions and orientations with respect to it. The carbonyl oxygens of all three appear to repel the carbonyl oxygen of Gly117, thus causing the peptide bond between Gly117 and Gly118 to undergo a peptide flip. As a consequence, the position of the main chain nitrogen of Gly118 in the "oxyanion" hole in the native enzyme becomes occupied by the carbonyl of Gly117. Furthermore, the flipped conformation is stabilized by hydrogen bonding of Gly117O to Gly119N and Ala201N, the other two functional elements of the three-pronged "oxyanion hole" characteristic of cholinesterases. All three inhibitors thus would be expected to abolish hydrolysis of all ester substrates, whether charged or neutral.
Huprine X is a novel acetylcholinesterase (AChE) inhibitor, with one of the highest affinities reported for a reversible inhibitor. It is a synthetic hybrid that contains the 4-aminoquinoline substructure of one anti-Alzheimer drug, tacrine, and a carbobicyclic moiety resembling that of another AChE inhibitor, (-)-huperzine A. Cocrystallization of huprine X with Torpedo californica AChE yielded crystals whose 3D structure was determined to 2.1 A resolution. The inhibitor binds to the anionic site and also hinders access to the esteratic site. Its aromatic portion occupies the same binding site as tacrine, stacking between the aromatic rings of Trp84 and Phe330, whereas the carbobicyclic unit occupies the same binding pocket as (-)-huperzine A. Its chlorine substituent was found to lie in a hydrophobic pocket interacting with rings of the aromatic residues Trp432 and Phe330 and with the methyl groups of Met436 and Ile439. Steady-state inhibition data show that huprine X binds to human AChE and Torpedo AChE 28- and 54-fold, respectively, more tightly than tacrine. This difference stems from the fact that the aminoquinoline moiety of huprine X makes interactions similar to those made by tacrine, but additional bonds to the enzyme are made by the huperzine-like substructure and the chlorine atom. Furthermore, both tacrine and huprine X bind more tightly to Torpedo than to human AChE, suggesting that their quinoline substructures interact better with Phe330 than with Tyr337, the corresponding residue in the human AChE structure. Both (-)-huperzine A and huprine X display slow binding properties, but only binding of the former causes a peptide flip of Gly117.
Allele frequencies for nine STR loci namely, D3S1358, HUMvWA, HUMFIBRA/FGA, D8S1179, D21S11, D18S51, D5S818, D13S317 and D7S820 were obtained from a sample of 198 unrelated Chinese in Beijing, China.
Allele frequencies for three STR loci, namely, CSF1PO, HUMTHO1 and TPOX, and the AMP-FLP locus D1S80 were obtained from a sample of 351 unrelated Chinese in Hong Kong.
The allele distributions at the 12 short tandem repeat (STR) loci D3S1358, HUMvWA, HUMFIBRA/FGA, HUMTHO1, HUMTPOX, HUMCSF1P0, D5S818, D13S317, D7S820, D8S1179, D21S11 and D18S51 have been determined for 284 unrelated Chinese in Hong Kong. The combined probability of identity for the 12 STR loci was about 4.1 x 10(-14) and the overall probability of excluding paternity 0.999978. None of the 12 loci were found to deviate from Hardy-Weinberg expectations according to the results of the exact test. There was also little evidence for association of alleles between loci. The results demonstrate that the loci are useful for forensic human identification and parentage testing for the Chinese population in Hong Kong.
BACKGROUND: Retinal artery occlusions typically result in sudden, unilateral painless loss of vision and may have varying presentations. They are associated with systemic diseases such as atherosclerosis, hypertension, and valvular heart disease. Additional risk factors include diabetes mellitus, cigarette smoking, giant-cell arteritis, and hyperlipidemia. They most often occur in persons 60 to 80 years of age. METHODS: Four patients have come to our clinics with varying degrees of visual loss as a result of retinal artery occlusions. The types of arteriolar occlusions presented include: precapillary arteriole occlusion, cilioretinal artery occlusion, branch retinal artery occlusion, and central retinal artery occlusion. RESULTS: Patients were followed for their ocular involvement, but also included was medical management of the underlying systemic disease condition. Workup of retinal artery occlusion included laboratory testing, carotid duplex scans, and echocardiograms to uncover the possible systemic etiologies of the artery occlusion. CONCLUSION: Optometrists should recognize the signs and symptoms of the various arterial obstructions and refer patients for systemic treatment as indicated. Patients who manifest retinal or pre-retinal artery occlusions should undergo thorough systemic evaluations for vascular disease, including: atherosclerotic disease, hypertension, and valvular heart disease.
STATEMENT OF PROBLEM: Acrylic resin complete dentures exhibit certain unavoidable dimensional changes. Processing shrinkage and expansion due to water uptake are 2 important aspects influencing dimensional accuracy. PURPOSE: This study investigated linear dimensional changes and water sorption of dentures processed by dry and wet heat with different rates of cooling. METHODS: Fine crosses marked on tinfoil inserts were placed at the incisive papilla and tuberosity regions of edentulous maxillary casts and incorporated into the dentures during polymerization by 3 processing techniques. A traveling microscope was used to measure the distances between the reference points to determine dimensional changes. Water uptake and content were determined by the mass changes of the dentures with an electronic balance. Data of linear dimensional change and water sorption were analyzed by multivariate analysis of variance and analysis of variance, respectively. Bonferroni simultaneous confidence intervals (95%) were applied for multiple comparison. RESULTS: Dry heat-processed and water bath-processed acrylic resin dentures did not exhibit significant differences in shrinkage (0.42% to 0.58%) at water saturation. Amounts of water sorption of dentures processed by dry and wet heat (0.50 and 0.48 mass%, respectively) were not significantly different, and their associated expansion did not entirely compensate for the processing shrinkage. The initial water content of dry heat-processed dentures (1.77 mass%) was unexpectedly slightly higher than that of wet heat-processed dentures (1.68 mass%). The rate at which the dentures cooled did not affect their initial water content and subsequent water uptake. CONCLUSIONS: Water uptake of dry and wet heat-processed acrylic resin dentures after deflasking was in both cases low, and the dentures did not reveal significant differences in shrinkage at water saturation. Air oven-processed and water bath-processed acrylic resin dentures show similar dimensional shrinkage at water saturation.
DNA specimens isolated from the blood samples of 209 unrelated Chinese persons were characterised with four probes, i.e. MS1 (D1S7), YNH24 (D2S44), pH30 (D4S139) and TBQ7 (D10S28), in conjunction with the restriction enzyme HaeIII to establish a population DNA-profile database. Each locus showed a fairly wide distribution of alleles and high heterozygosity. The sizes of alleles ranged between 0.73 and 19.95 kb for the D1S7 locus, between 0.78 and 4.72 kb for the D2S44 locus, between 2.53 and 15.74 kb for the D4S139 locus, and between 0.66 and 6.53 kb for the D10S28 locus. The heterozygosities for the D1S7, D2S44, D4S139 and D10S28 loci were 97.6%, 92.3%, 86.6% and 96.2%, respectively. Allele frequencies were determined using the "fixed-bin' approach. The bins were based on the 30-band pattern of the molecular size marker used in this laboratory (GIBCO BRL 4401SA). The most commonly observed bin frequencies for the four loci ranged from 9% to 19%. When a default minimum bin frequency of 10% and the product rule based upon the principles of Hardy-Weinberg equilibrium were used to calculate the most common genotype frequencies, the values ranged from 2.1% to 6.4%. The minimum composite discriminating potential of the four loci, expressed as the product of the frequency of the most common genotype for each locus, was about 1 in 770,000.
Contact lens patient discomfort has been linked to the pH of lens care solutions differing from that of tears. To determine if this is a potential problem with multi-purpose soft contact lens solutions, we used a Fisher Scientific Accumet 950 pH/ion meter (accuracy +/- 0.05 pH units) to measure the pH of 3 multi-purpose solutions-Alcon's Opti-One, Allergan's Complete, and Bausch & Lomb's ReNu. The resulting pH values were compared to the threshold for ocular awareness, which is outside the zone of 6.6 to 7.8, and the pH value of tears of 7.45. Each solution was dispensed and measured daily over a 23- to 36-day period using 15-ml increments to simulate the amount used on a daily basis. The average pH of solutions tested were 7.18 +/- 0.02 for ReNu, 6.97 +/- 0.02 for Opti-One, and 7.55 +/- 0.02 for Complete. The highest and lowest pH values of all three multi-purpose solutions were found to be within the zone of ocular comfort and remained within a narrow value range throughout the testing period. Therefore, pH-induced discomfort is unlikely to occur when using these solutions on a daily basis. Nonetheless, practitioners should select lens care products carefully to ensure that the prescribed regimen meets the patient's needs.
Three-way DNA junctions were synthesized with class-IIS restriction endonuclease (ENase) recognition sites and potential cleavage sites located on separate arms. Cleavage was investigated with junctions labeled in each of the three strands. BpmI and BsaI failed to cleave either strand of either arm, whereas BsmAI cleaved one strand. FokI and HphI cleaved both strands of both arms at the expected nucleotide positions. FokI cleavage was independent of the spacing between the recognition site and the junction. This new activity of class-IIS ENases may be useful for investigating branched DNA structures.
Sequences of the recA genes of the highly divergent thermopholic eubacteria Thermus aquaticus (and Thermus thermophilus), Thermotoga maritima, and Aquifex pyrophilus were determined from fragments derived by polymerase chain reaction (PCR) with degenerate primers and from inverse PCR products obtained using unique primers based on the fragment sequences. The source of the PCR products was verified by Southern hybridization. Complete PCR-derived recA genes were cloned into an expression vector regulated by a temperature-sensitive lambda-repressor, and independently derived clones expressing thermostable recA were selected. DNA sequences were verified to be authentic by direct cycle-sequencing of PCR products and/or sequencing of several clones. In contrast to Escherichia coli RecA protein, all the purified thermophilic RecA proteins exhibited single-stranded DNA-dependent ATPase activity optima above 70 degrees C. Phylogenetic analysis of RecA sequences suggested that the thermophilic RecA proteins were at least as different from one another as were Gram-positive organisms, mesophilic Gram-negative organisms, and cyanobacteria. In spite of substantial sequence divergence, interesting characteristics of the thermostable RecA proteins included increased valine content, common amino acid replacements at two highly conserved sites, and an increase in the calculated isoelectric point of approximately a full pH unit.
Genomic clones containing human delta-aminolevulinate dehydratase (ALAD), the second enzyme in the heme pathway, were isolated, and the entire sequence was determined in both orientations (15,913 bp; GenBank Accession No. X64467). The gene contained two alternative noncoding exons, 1A and 1B, and 11 coding exons, 2-12. Ten Alu-repetitive elements were within the gene, including an inverted repeat that may have resulted from gene conversion. The housekeeping transcript, which included exon 1A and not 1B, was identified in a human adult liver cDNA library, while an erythroid-specific transcript, which contained exon 1B and not 1A, was detected in a human K562 erythroleukemia cDNA library. The promoter region upstream of housekeeping exon 1A was GC-rich and contained three potential Sp1 elements and a CCAAT box. Further upstream, there were three potential GATA-1 binding sites and an AP1 site. The promoter region upstream of erythroid-specific exon 1B had several CACCC boxes and two potential GATA-1 binding sites. To assess the tissue-specific expression of exons 1A and 1B, HeLa and K562 cells were transduced with CAT constructs containing either exon 1A or 1B and their respective upstream promoter region. Two housekeeping CAT constructs, with 450 and 1400 bp upstream of exon 1A, were expressed at similar levels in HeLa cells, whereas the erythroid-specific construct, containing the entire 450-bp promoter region upstream of exon 1B, was not. In contrast, the housekeeping and erythroid constructs were both expressed in K562 cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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Branch capture reactions (BCR) contain three DNA species: (i) a recipient restriction fragment terminating in an overhang, (ii) a displacer strand containing two adjacent sequences, with one complementary to the overhang and to contiguous nucleotides within the recipient duplex and (iii) a linker which is complementary to the second displacer sequence. Branched complexes containing all three species may be captured by ligation of the linker to the recipient overhang. The use of 5-MedC in the displacer facilitates BCR. High temperature ligation with a thermostable enzyme increased specificity for ligation to the correct recipient in a complex mixture of restriction fragments. Displacer synthesis by PCR permitted separate reactions of formation of stable displacement complexes and of high-temperature ligation. Ethylene glycol-containing buffer permitted PCR with 5-MedCTP or high G + C products using thermostable polymerases. BCR may be used to modify the ends of one recipient DNA duplex in a population of duplex DNA fragments. Modification of the recipient could be used to facilitate detection, affinity chromatography or cloning. By using PCR to obtain a BCR displacer, the sequence non-homologous to the recipient duplex may be expanded to include the sequence of a selectable marker, thus facilitating chromosome walking.
Coinfection with Mycoplasma fermentans (incognitus strain) enhances the ability of human immunodeficiency virus type-1 (HIV-1) to induce cytopathic effects on human T lymphocytes in vitro. Syncytium formation of HIV-infected T cells was essentially eliminated in the presence of M. fermentans (incognitus strain), despite prominent cell death. However, replication and production of HIV-1 particles continued during the coinfection. Furthermore, the supernatant from cultures coinfected with HIV-1 and the mycoplasma contained a factor that inhibited the standard reverse transcriptase enzyme assay. The modification of the biological properties of HIV-1 by coinfection with mycoplasma may be involved in the pathogenesis of acquired immunodeficiency syndrome (AIDS).
The effect of anoxia on roots of soybean (Glycine max [L.] Merr., variety ;Williams') was studied at various levels and the results compared to those from previously studied species. While alcohol dehydrogenase (ADH) activity is induced in a manner similar to other plant species, other aspects of the anaerobic response are unique to soybean. A variety of molecular clones was used to analyze changes in soybean and maize RNA levels. Increased RNA accumulation was observed in both species with a maize ADH clone, while a maize aldolase and one of the two different maize glyceraldehyde-3-phosphate dehydrogenase cDNA clones showed induction only in maize. A maize sucrose synthase 1 clone showed induction in maize but no hybridization to soybean RNA samples. The reduction in the number of anaerobically inducible soybean genes relative to maize is consistent with in vivo and in vitro protein synthesis results. Only four major proteins are labeled during anoxia in soybean, one corresponding to ADH, while maize has been reported to have about 20. In either species, in vitro translation yields similar products with RNA from anaerobic and pre-stress plants, indicative of translational control during anoxia. These results are discussed in relation to the differential tolerance of maize and soybean to anaerobic stress.