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Biomedical subjects

E Choi

Publications and source records attributed to E Choi.

At least 91 records · Page 5Linked to original sources
PubMed1991

HLA-DQA1*0101 haplotypes and disease outcome in early onset pauciarticular juvenile rheumatoid arthritis.

To further investigate a clinical impression that patients with early onset pauciarticular juvenile rheumatoid arthritis (EOPA-JRA) who carry HLA-DQw1 have more severe arthritis, we subtyped HLA-DQw1 in American midwestern patients with EOPA-JRA. The HLA-DQA1*0101 subtype was present in 10 of 19 patients who developed persistent polyarticular erosive disease compared with 18 of 92 healthy controls (chi 2 = 9.13, p = 0.003, RR = 4.6), and occurred more frequently in this polyarticular group than in patients without polyarticular erosive disease (chi 2 = 4.11, p = 0.040, RR = 3.0). The presence of HLA-DQA1*0101 was significantly lower in patients with chronic iridocyclitis than in patients without chronic iridocyclitis (chi 2 = 7.07, p = 0.008, RR = 0.21). In HLA-DQA1*0101 positive patients, DNA sequences of the beta-1 domain of the HLA-DQ alpha and HLA-DQ beta genes (HLA-DQA1*0101, HLA-DQB1*0501 and HLA-DQB1*0503) were identical to those in controls. In this midwestern EOPA-JRA population, HLA-DQA1*0101 or genes in linkage disequilibrium with it, are associated with a cohort of patients with EOPA-JRA with distinct clinical characteristics.

Alleles↗
PubMed1990

A distinct HLA-DRw8 haplotype characterizes patients with juvenile rheumatoid arthritis.

We studied the first domain of the HLA-DRB1, HLA-DQA1, and HLA-DQB1 loci of 67 HLA-DRw8-positive Caucasians including 43 with early-onset pauciarticular juvenile rheumatoid arthritis (EOPA-JRA, alternatively known as early-onset pauciarticular juvenile chronic arthritis). Serology, restriction fragment length polymorphism (RFLP), and polymerase chain reaction (PCR) oligotyping revealed that 62, including all the EOPA-JRA patients, carried the HLA-DRB1*0801, DQA1*0401, DQB1*0402 genotype. Approximately one-fifth of the controls carried atypical HLA-DRB1, HLA-DQA1, and/or HLA-DQB1 loci on their HLA-DRw8 haplotype confirmed by family studies. DNA sequences of HLA-DRB1, DQA1, and DQB1 alleles in patients and controls were identical to those previously reported. Disease association studies in 113 EOPA-JRA patients and 207 controls unselected for HLA-DRw8 revealed that the HLA-DRB1*0801, DQA1*0401, DQB1*0402 genotype was associated with a higher relative risk (RR) for disease (RR = 12.8, chi 2 = 48.8, P less than 10(-4)) than was the serologically defined presence of HLA-DRw8 (RR = 8, chi 2 = 39, P less than 10(-4)). Further analysis suggested that the DQ genes on HLA-DRw8 haplotypes are as likely as the DR genes to contribute to the pathogenesis of EOPA-JRA. This study increases to five the number of HLA-DR/DQ haplotypes identified in HLA-DRw8 Caucasians.

Arthritis, Juvenile↗
PubMed1990

Uniparental isodisomy 6 associated with deficiency of the fourth component of complement.

We identified an extremely rare condition, isolated complete deficiency of the fourth component of complement, in a child with systemic lupus erythematosus. The genes for C4 are located within the major histocompatibility complex (MHC) on the short arm of chromosome 6. The patient expressed only paternal phenotypes for proteins encoded by the MHC (HLA and GLO), yet was 46XX with no detectable 6p deletion. Genomic DNA from patient, parents, and sibling was digested with restriction enzymes, and blots were probed for five chromosome 6 markers. At all loci, maternal and paternal RFLPs could be distinguished, and the patient showed only paternal bands. RFLP analysis of markers from four other chromosomes showed maternal and paternal contribution. The data are consistent with uniparental isodisomy 6 (inheritance of two identical chromosome 6 haplotypes from the father and none from the mother). Direct analysis of genetic material from both parents, as well as detection of multiple protein polymorphisms encoded on chromosome 6, clearly demonstrates this novel mechanism for the expression of a recessive genetic condition.

Blotting, Southern↗
PubMed1989

Ascorbic acid, HDL cholesterol, and apolipoprotein A-I in an elderly Chinese population in Boston.

The relationships between plasma HDL cholesterol, apolipoprotein A-I, and plasma ascorbic acid were examined in 146 women and 92 men in a Chinese population in Boston, aged 60 and above. A significant partial correlation (r = 0.21, p = 0.015) between plasma ascorbic acid and plasma HDL cholesterol was observed among (predominantly nonsmoking) females after the effects of potentially confounding variables were taken into account. A similar relationship among 26 nonsmoking men was suggestive but inconclusive; there was no evidence of a relationship among 66 male smokers. The partial correlation between plasma apolipoprotein A-I and plasma ascorbic acid was marginally significant for women (r = 0.22, p = 0.057, n = 87) but was highly significant for men (r = 0.43, p = 0.007, n = 51). The correlation coefficient for men was highly dependent on smoking status, being 0.80 for those who never smoked and almost zero for current smokers.

Aged↗
PubMed1989

An intronic 10-base-pair deletion in a class II A beta gene affects RNA processing.

Several biologically important examples of posttranscriptionally regulated genes have recently been described (T. Gerster, D. Picard, and W. Schaffner, Cell 45:45-52, 1986; R. Reeves, T.S. Elton, M.S. Nissen, D. Lehn, and K.R. Johnson, Proc. Natl. Acad. Sci. USA 84:6531-6535, 1987; H.A. Young, L. Varesio, and P. Hwu, Mol. Cell. Biol. 6:2253-2256, 1986). Little is known, however, regarding sequences that mediate posttranscriptional RNA stability. Characterization in our laboratory of a mutant murine B lymphoma, M12.C3, revealed a posttranscriptional defect affecting the synthesis of a major histocompatibility complex class II gene (A beta d) whose product normally controls both the specificity and magnitude of the immune response. Molecular studies revealed that the mutation responsible for diminished A beta d gene expression was an intronic deletion of 10 base pairs (bp) located 99 bp 5' of the third exon. This deletion lies in a region not known to be critical for accurate and efficient splicing. Furthermore, sequence analysis of amplified A beta-specific cDNA demonstrated that the small number of A beta d transcripts produced in the mutant cells was correctly spliced. It appears that the mechanism by which this intronic 10-bp deletion acts to decrease RNA stability is unlikely to be at the level of RNA splicing.

Animals↗
PubMed1989

Regulation of apolipoprotein E synthesis and mRNA by diet and hormones.

Rats were fasted or fasted and refed simple purified diets so the effects of individual carbohydrates or fats could be studied. Freshly isolated hepatocytes from these animals were used to measure both apoE synthesis and mRNA levels so any changes in apoE synthesis that might occur without changes in its mRNA could be detected. Some of these experiments were done with both sexes. Both fasting and fasting and refeeding a 60% glucose fat-free diet significantly increased spoE synthesis. However, cyclic AMP is not likely to rapidly mediate the effect of fasting since dibutyryl cAMP slightly lowered (rather than increased) apoE synthesis and mRNA when injected into rats for 4.5 h. Dietary fat had no effect either in the absence of carbohydrate or when consumption of carbohydrate was constant in pair-fed rats. ApoE mRNA levels remained normal for 4 days in primary hepatocytes cultured in medium that had only amino acids as an energy source. Added hormones or fructose had no significant effect. Thus, only fasting and fasting and refeeding glucose were able to significantly change apoE synthesis or mRNA levels. Synthesis of apoE may be regulated to increase when apoE is secreted with very low density lipoprotein or when apoE in secreted high density lipoprotein is needed to acquire cholesteryl esters for the synthesis of bile salts and acids by liver.

Animals↗
PubMed1987

Isolation of a protein C activator from southern copperhead venom.

A protease from the venom of the Southern Copperhead snake (Agkistrodon contortrix contortrix) that activates protein C was purified to homogeneity by a combination of sulfopropyl (SP)-Sephadex C-50, Sephadex G-150 and Mono-S column chromatography. The purified enzyme is a glycoprotein, and migrated as a single band in sodium dodecylsulfate-polyacrylamide gel electrophoresis with an apparent molecular weight of 37,000 under non-reducing conditions. Upon reduction with 2-mercaptoethanol, the enzyme exhibited a Mr of 40,000. The purified enzyme prolonged the clotting time of human plasma in a dose- and temperature-dependent manner. Purified bovine protein C was completely activated within 10 minutes upon incubation with the purified protease at a 1:500 enzyme: substrate ratio. This reaction was markedly inhibited by calcium ions. The purified venom protein C activator had no effect on human fibrinogen.

Animals↗
PubMed1987

Demonstration of human papillomavirus DNA in oral condyloma acuminatum.

Condyloma acuminatum arising on oral mucous membranes exhibits distinct histopathological features that allow for differentiation from the more common squamous papilloma. These lesions are parakeratinized with cryptic invagination of cornified cells extending into an acanthotic spinous cell layer. Superficial spinous layer koilocytosis is a prominent feature and the condylomatous papillomas exhibit a tendency for sessile architecture. Among 62 instances, the average age was 39.7 years with a predilection for the 3rd and 4th decades. The male to female ration was 5.7:1 and the tongue, gingiva and lips were the favored sites. Whereas 25% of the evaluated cases demonstrated upper spinous layer papillomavirus common antigen immunoreactivity, DNA in situ hybridization under conditions of high stringency disclosed the presence of human papillomavirus Types 6, 11 or related genomes in 85% of the lesions. A single case was found to harbor human papillomavirus Type 2.

Adolescent↗
PubMed1986

Identification of functional regions on the I-Ab molecule by site-directed mutagenesis.

Functional analysis of mutant class II major histocompatibility complex molecules has begun to identify regions important for antibody binding and for T-cell activation. By using in vitro mutagenesis directed at the beta 1 domain of the Ab beta gene we have constructed three structurally distinct mutant Ab beta genes. Each of these genes, as well as the wild-type Ab beta gene, was cotransfected together with the wild-type Ab alpha gene into the Ia-negative B-lymphoma cell line M12.C3. Transfection resulted in the successful synthesis and cell surface expression of three mutant class II antigens that showed serological and functional alterations as compared to the I-Ab antigens from the M12.C3 cell transfected with the wild-type gene. The variable patterns of both I-Ab-specific monoclonal antibody binding and activation of I-Ab-specific T-cell hybridomas show that the mutations result in the loss of structural epitopes required for both monoclonal antibody binding and for T-cell recognition. The data suggest that there are multiple sites on a single Ia molecule that are recognized by T helper cells and also that the tertiary conformation of the Ia molecule can be critical in the formation of such sites.

Animals↗
PubMed1986

L-histidine inhibits the growth of Ehrlich ascites tumour.

The in vitro studies on the growth of cultured Ehrlich ascites tumour cells showed similar results as the in vivo studies reported previously. The growth of tumour cells was inhibited when cultured in 0.02 or 0.03 M L-histidine. At these concentrations, L-glycine shows no significant effect.

Animals↗
PubMed1985

Complex regulation of class II gene expression: analysis with class II mutant cell lines.

Several Ia-negative variants of a homozygous Iad-expressing antigen-presenting B lymphoma cell line, M12, have been obtained by repeated cycles of negative immunoselection after mutagenesis with ethylmethane sulfonate or gamma-irradiation. Two such Iad-negative cell lines, selected with a mixture of alpha I-Ad and alpha I-Ed monoclonal antibodies, failed to present antigen to all cloned Iad-restricted T cells tested, whereas the third cell line, selected with alpha I-Ad reagents only, stimulated I-Ed but not I-Ad-restricted T cells. The mutations in all three cell lines resulted in the absence of RNA specific for the A beta d gene. In addition, two-dimensional gel electrophoresis of immunoprecipitates from one of the I-Ed-negative cell lines demonstrated the presence of intracytoplasmic Ed polypeptides that exhibited significantly decreased amounts of oligosaccharide-induced heterogeneity. The introduction of class II A beta b and A alpha b genes by DNA-mediated transfection resulted in the serologic and functional expression of a class II I-Ab molecule but not the reexpression of the endogenous class II molecules; thus a transacting regulatory element is unlikely to be the target of the mutagenic event. The analysis of these and other Ia variant cell lines may prove useful in understanding the molecular mechanisms that control the expression of class II molecules in B cells.

Animals↗
PubMed1985

DNA-mediated transfer of major histocompatibility class II I-Ab and I-Abm12 genes into B lymphoma cells: molecular and functional analysis of introduced antigens.

A20.2J B lymphoma cells have been co-transfected with the A alpha b, A beta b or with the A alpha b, A beta bm12 and neomycin resistance genes. The transfected cell lines constitutively express the I-Ab or I-Abm12 class II molecules at a level comparable with that of the endogenous I-Ad antigen. The I-Ab antigens expressed on three independently transfected B cell clones (A20.Ab.1, A20.Ab.2, and A20.Ab.3) are serologically and functionally indistinguishable from the I-Ab molecules expressed by control H-2bxd B hybridoma cells (LB cells). These transfected cell lines were potent I region-restricted antigen-presenting cells to a large panel of antigen-specific, autoreactive and alloreactive T cell hybridomas, as well as normal T cell clones. There were not significant differences in the efficiency of antigen presentation by the Ia molecules encoded by the transfected, as compared with the endogenous, I-A genes. The expression of a functional I-Ab antigen on the surface of cells transfected with A beta bm12 and A alpha b genes is consistent with previous work that implicated the A beta-chain alone in the bm 12 mutation. Furthermore, because the transfected A20.Ab and A20.Abm12 cells display the serologic and functional properties of normal spleen cells from the wild-type and mutant mouse strains, respectively, it is clear that class II genes do not undergo unexpected and unpredictable alterations after transfection in this system. This system permits us to investigate the structural requirements for interactions between class II major histocompatibility complex antigens, a foreign antigen, and the T cell receptor by in vitro site-directed mutagenesis coupled with DNA-mediated gene transfer.

Animals↗
PubMed1984

The structure of rat preproatrial natriuretic factor as defined by a complementary DNA clone.

The structure of rat preproatrial natriuretic factor ( preproANF ) was determined by nucleotide sequence analysis of an ANF complementary DNA clone. PreproANF is composed of a hydrophobic leader segment (20 amino acids), a precursor containing one glycosylation site (106 amino acids), and ANF (24 amino acids). Atrial natriuretic factor is located at the carboxyl terminus of the precursor molecule. The human, mouse, and rat genomes each contain a single ANF gene which is highly conserved.

Animals↗