Search PubMed⌕ Search

Biomedical subjects

E M Tan

Publications and source records attributed to E M Tan.

At least 199 records · Page 11Linked to original sources
PubMed1985

Synthesis of small nuclear ribonucleoprotein particles by the malarial parasite Plasmodium falciparum.

Sera from patients with autoimmune diseases have been used to identify small nuclear ribonucleoprotein particles (snRNPs) present in higher eukaryotic cells and also in dinoflagellates. Previously these sera have not detected crossreactive snRNP protein antigens of other lower eukaryotes such as yeast, Tetrahymena, or Dictyostelium. We report that anti-Sm, anti-U1-RNP, and anti-La/SS-B human antisera react with specific snRNP protein antigens synthesized by the protozoan Plasmodium falciparum, the human malarial parasite. These results suggest that the structure and antigenicity (and thus probably the function) of snRNPs have been widely conserved in eukaryote evolution.

Animals↗
PubMed1985

Effect of actinomycin D on the expression of nuclear antigen SS-B/La.

The nuclear autoantigen SS-B/La, which is recognized by antibodies in certain autoimmune diseases, is complexed with distinct cellular RNAs and the complex of antigen-RNA profile remains constant throughout the cell cycle. This antigen is prominent in the nucleolus during G1/S phase of the cell cycle. Actinomycin D at a concentration of 0.0005 microgram/ml is capable of abolishing the appearance of SS-B/La in the nucleolus. The amount of immune-precipitable SS-B/La-associated RNAs is reduced by 0.005 microgram/ml actinomycin D treatment. The mechanism for these findings is suggested to be related to inhibition of the synthesis of messenger RNA coding for SS-B/La.

Antigens↗
PubMed1985

Modulation of procollagen gene expression by retinoids. Inhibition of collagen production by retinoic acid accompanied by reduced type I procollagen messenger ribonucleic acid levels in human skin fibroblast cultures.

Recent clinical observations have suggested that retinoids, which are in frequent use in dermatology, can affect the connective tissue metabolism in skin and other tissues. In this study, we examined the effects of several retinoids on the metabolism of collagen by human skin fibroblasts in culture. Incubation of cultured fibroblasts with all-trans-retinoic acid or 13-cis-retinoic acid, in 10(-5) M or higher concentrations, markedly reduced the procollagen production, as measured by synthesis of radioactive hydroxyproline. The effect was selective in that little, if any, inhibition was noted in the incorporation of [3H]leucine into the noncollagenous proteins, when the cells were incubated with the retinoids in 10(-5) M concentration. Similar reduction in procollagen production was noted with retinol and retinal, whereas an aromatic analogue of retinoic acid ethyl ester (RO-10-9359) resulted in a slight increase in procollagen production in these cultures. The reduction in procollagen production by all-trans-retinoic acid was accompanied by a similar reduction in pro alpha 2(I) of type I procollagen specific messenger RNA (mRNA), as detected by dot blot and Northern blot hybridizations. Hybridizations with human fibronectin and beta-actin specific DNA probes indicated that the levels of the corresponding mRNAs were not affected by the retinoids, further suggesting selectivity in the inhibition of procollagen gene expression. Further control experiments indicated that all-trans-retinoic acid, under the culture conditions employed, did not affect the posttranslational hydroxylation of prolyl residues, the mannosylation of newly synthesized procollagen, the specific radioactivity of the intracellular prolyltransfer RNA pool, or DNA replication. All-trans-retinoic acid also elicited a reduction in trypsin-activatable collagenase, but not in the activity of prolyl hydroxylase or an elastaselike neutral protease in the fibroblast cultures. Incubation of three fibroblast lines established from human keloids with all-trans-retinoic acid or 13-cis-retinoic acid also resulted in a marked reduction in procollagen production. The results, therefore, suggest that further development of retinoids might provide a novel means of modulating collagen gene expression in patients with various diseases affecting the connective tissues.

Cells, Cultured↗
PubMed1985

Purification and N-terminal amino acid sequence of proliferating cell nuclear antigen (PCNA)/cyclin and development of ELISA for anti-PCNA antibodies.

Proliferating cell nuclear antigen (PCNA), also called cyclin, was purified from PBS extract of rabbit thymus by using a combination of ammonium sulfate fractionation, DEAE-Sephacel, HPLC ion exchange, and HPLC gel filtration column chromatography. PCNA was purified more than 600 times and was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. SDS-PAGE showed that a 36 kD protein was selectively isolated in this purification process, and this protein was identified as PCNA by immunoblotting. Other previously identified nuclear antigens, Sm, nRNP, SS-A/Ro, SS-B/La, histone, and DNA, were not detected in this preparation by counterimmunoelectrophoresis and enzyme-linked immunosorbent assay (ELISA). Purified PCNA was used as an antigen to develop ELISA for rapid and specific detection of anti-PCNA in human sera. For further purification, the 36 kD band was electrophoretically eluted from SDS gel slices. The amino acid composition and the first 25 residues from the N-terminus of the protein were determined by using electroeluted PCNA. This amino acid sequence was found to be unique and showed little sequence homology with existent proteins in the protein identification resources databank.

Amino Acid Sequence↗
PubMed1985

Phenytoin modulates connective tissue metabolism and cell proliferation in human skin fibroblast cultures.

Phenytoin has been proposed for the treatment of certain dermatologic conditions involving connective tissue abnormalities. To understand the biochemical basis of connective tissue changes, we incubated human skin fibroblasts in culture with varying concentrations of phenytoin. The results indicated that fibroblast proliferation, detected by tritiated thymidine incorporation into cells, was slightly stimulated when short incubation periods and low concentrations of phenytoin were employed. However, with longer incubation times and higher phenytoin concentrations, a significant reduction in fibroblast proliferation was observed. Further studies demonstrated that incubation of cells with phenytoin did not affect the production of procollagen, measured as synthesis of radioactive hydroxyproline in the cultures. However, assay of prolyl hydroxylase, an enzyme participating in the post-translational synthesis of hydroxyproline during collagen biosynthesis, was significantly reduced in the fibroblast cultures. The activity of collagenase, an enzyme participating in degradation of collagen, was markedly decreased in cultures treated with phenytoin. Thus, phenytoin may modulate collagen metabolism primarily by affecting the degradation of collagen. The results support previous suggestions that phenytoin may be useful for treatment of patients with increased levels of collagenase, such as in recessive dystrophic epidermolysis bullosa.

Cell Division↗
PubMed1985

Identification of ribosomal protein autoantigens.

Approximately 20% of patients with systemic lupus erythematosus and with anti-Sm autoantibodies synthesize autoantibodies, called anti-rRNP, to components of the ribosome. We found that anti-rRNP sera reacted predominantly with three ribosomal phosphoproteins of approximate Mr = 38,000, 16,000 and 15,000, both by immunoprecipitation and by immunoblotting. The human autoantibodies cross-reacted with similar antigens present in rodent, brine shrimp, and yeast cells but reacted weakly if at all with proteins of bacteria. Thus the human autoantibodies recognize epitopes that are widely conserved in evolution. Purified ribosomal proteins together with specific rabbit antisera were used to identify the two smaller rRNP antigens as the acidic phosphoproteins of the large ribosomal subunit, designated P1/P2(L40/L41) (rat), eL7/eL12 (Artemia, brine shrimp), and A1/A2 (yeast). These proteins function in the elongation step of protein synthesis in an analogous fashion to the L7/L12 ribosomal proteins of E. coli. The 38,000-dalton rRNP antigen corresponds to a nonacidic protein also associated with the large ribosomal subunit. The human autoantibodies appear to have a specificity similar to that of a previously described mouse monoclonal antibody obtained from mice injected with heterologous (chick) ribosomes, suggesting that both the human polyclonal autoantibodies and the mouse monoclonal recognize a class of epitope(s) that is common in all three ribosomal proteins. In addition, we found that many of the anti-ribosomal sera contained a further class of autoantibodies reactive with naked RNA. These may be similar to the anti-RNA antibodies previously described in both humans and mice with autoimmune disease.

Animals↗
PubMed1985

Purification of the Sm nuclear autoantigen. Detection and clinical significance of IgM antibody.

Sm antigen from rabbit thymus acetone powder was purified using a combination of ammonium sulphate precipitation, DEAE-Sephacel and hydroxyapatite chromatography. This preparation was devoid of previously identified nuclear antigens including ribonucleoprotein (U1-RNP), proliferating cell nuclear antigen (PCNA), Sjögren's syndrome antigen A (SS-A/Ro), Sjögren's syndrome antigen B (SS-B/La), Sjögren's lupus antigen (SL), scleroderma antigen 70 (Scl-70), DNA and histones. The purified material was used in an enzyme linked immunosorbent assay (ELISA) to detect anti-Sm antibody. All sera with precipitating Sm antibody detected by immunodiffusion gave reactions in ELISA greater than 0.40 OD405 and contained predominantly IgG anti-Sm antibody. Of 112 sera which did not have anti-Sm by immunodiffusion there were five which gave reactions greater than 0.40 OD405. Four of these five sera contained only IgM antibody and the fifth contained both IgM and IgG. Of these five, one came from a 'normal' control who had a positive anti-nuclear antibody (ANA), facial rash and diabetes, two were from patients with systemic lupus erythematosus (SLE) and two were from patients with mixed connective tissue disease (MCTD). These findings demonstrate that there are patients whose anti-Sm response may be restricted to IgM and in some of these patients the clinical presentation may be different from that of classical SLE.

Animals↗
PubMed1984

Identification of the SS-A/Ro intracellular antigen with autoimmune sera.

Autoantibodies to SS-A/Ro antigen have been described in the sera of certain patients with Sjögren's syndrome, systemic lupus erythematosus and in neonates with lupus and/or congenital heart block. SS-A/Ro is a trypsin-sensitive intracellular antigen which appears to be associated with another intracellular antigen SS-B/La in tissue extracts. This study describes a simple method of separation of SS-A/Ro and SS-B/La antigenic activity by differential salt elution in polybuffer ion exchange chromatography. The partially purified SS-A/Ro antigen was separated by polyacrylamide gel electrophoresis under non-denaturing conditions and identified by Western blot analysis as a single polypeptide of 61,000 Da. The pI of SS-A/Ro antigen was 4.67. The partially purified SS-A/Ro antigen derived from gel electrophoresis could be adapted to an enzyme linked immunosorbent assay (ELISA) for the detection of antibody.

Antigens↗
PubMed1984

Multiple autoantigen binding capabilities of mouse monoclonal antibodies selected for rheumatoid factor activity.

We report that approximately 1/4 of monoclonal rheumatoid factors produced by hybridomas derived from fusions of spleen cells from MRL/lpr/lpr mice with systemic lupus erythematosus (SLE) and arthritis exhibited multiple reactivities with other autoantigens, including dDNA , histones, and/or cytoskeletal-cytoplasmic elements. The patterns of reactivities of most of these clones differed, indicating that each had a separate B cell ancestor. Studies with eluted antibodies demonstrated that a single species of antibody molecules was responsible for the observed multiple reactivities. Inhibition experiments suggested that an antibody combining site may be large enough to accommodate dissimilar epitopes. These findings may provide further insights into the generation and extent of antibody diversity as well as the etiopathogenesis of systemic autoimmune diseases.

Animals↗
PubMed1984

Characterization of proliferating cell nuclear antigen recognized by autoantibodies in lupus sera.

A nuclear antigen associated with cell proliferation (proliferating cell nuclear antigen [PCNA]) and blast transformation is recognized by autoantibodies in the sera of some patients with systemic lupus erythematosus. Using this autoantibody as a reagent, PCNA was purified 120-fold by ammonium sulfate fractionation, DEAE chromatography, and Sephadex G200 gel filtration. The antigenicity of PCNA was sensitive to trypsin but resistant to ribonuclease and deoxyribonuclease, suggesting that the antigenic determinant resided in protein and not nucleic acids. PCNA was inactivated at 56 degrees C for 30 min. Isoelectrophoretic focusing showed that the pI was 4.8. Analysis of immunoprecipitates on polyacrylamide gels showed the presence of IgG heavy and light chains and a single polypeptide band of 33,000 mol wt. This polypeptide band was the reactive antigen in immunoblotting (Western transfer) assays.

Animals↗
PubMed1984

The importance of tissue substrate in the SS-A/Ro antigen-antibody system.

Using highly monospecific anti-SS-A containing sera and specific antibody to SS-A antigen dissociated from immune precipitates, tissue sections and cell culture lines were evaluated by the indirect immunofluorescence technique to determine the intracellular location, tissue distribution, and species specificity of the SS-A/Ro antigen. The SS-A/Ro antigen is predominantly a nuclear antigen giving an immunofluorescence staining pattern of discrete nuclear speckles. The SS-A/Ro antigen is present in a wide variety of human tissue, including kidney and liver parenchymal cells, lymphocytes, fibroblasts, and epithelioid cells. However, the SS-A/Ro antigen does appear to have a variable species distribution, with significant quantities of the antigen detected by immunofluorescence in cells of human, monkey, dog, and guinea pig, but absent to low amounts detected in cells of mouse, rat, rabbit, hamster, and chicken.

Animals↗
PubMed1984

Antibodies to a nuclear/nucleolar antigen in patients with polymyositis overlap syndromes.

A precipitating antigen-antibody system has been characterized that occurs in patients with polymyositis. At least half of the patients not only have polymyositis but also have scleroderma. The proposed name for this antigen found in calf thymus extract (CTE) is PM-Scl, to indicate the almost universal presence of polymyositis and the frequent occurrence of scleroderma in the patients who make antibodies to this antigen. The antigen is probably nucleolar since all sera which precipitate with the PM-Scl antigen stain the nucleoli of Hep2 cells by indirect immunofluorescence. The PM-Scl immune system is a distinctive one different from the other known precipitins that occur in patients with polymyositis and dermatomyositis including Jo1, nRNP, and Mi. This PM-Scl antigen and its antibody represent one system which constitutes part of the reactions previously designated as PM1. Interlaboratory exchange of sera and extracts have established the unique nature of this reaction which occurs in patients with inflammatory myopathy.

Antigen-Antibody Reactions↗
PubMed1984

The role of RNP, Sm, and SS-A/Ro-specific antisera from patients with lupus erythematosus in inducing antibody-dependent cellular cytotoxicity (ADCC) of targets coated with nonhistone nuclear antigens.

To better understand potential antibody-dependent mechanisms of tissue damage in lupus erythematosus (LE), an examination of whether antibodies to nonhistone nuclear antigens in LE patients' sera can induce ADCC of cellular targets coated with the corresponding antigens was undertaken. With high titer anti-RNP sera, significant ADCC was seen with monocyte (P less than 0.01), T-lymphocyte (P less than 0.001), and low-density lymphocyte (P less than 0.001) effectors. Using monocyte effectors, significant ADCC was seen with anti-RNP (P less than 0.01), anti-Sm (P less than 0.01), and anti-SSA/Ro (P less than 0.01), with the most profound lysis being with the anti-SSA/Ro sera. Neutrophils were ineffective in any nuclear antigen-antibody system tested. The effective mononuclear cell-mediated ADCC seen with anti-RNP, anti-Sm, and anti-SSA antisera may be related to the mononuclear cell-associated tissue change seen in cutaneous lupus lesions.

Antibodies↗
PubMed1984

Autoallergic reactions induced by procainamide.

Procainamide has a high propensity for the induction of an autoimmune response. The immune response is highly selective and the autoantibodies so induced are directed against nuclear histones. Acetylator phenotypes play an important role in the immune response, with slow acetylators developing antihistone antibodies much sooner than fast acetylators. In the early detection of drug-induced lupus syndromes, the finding of antihistone antibodies in the absence of other types of antinuclear antibodies greatly aids in establishing the diagnosis.

Acetylation↗
PubMed1984

Standardization of the immunofluorescence test for autoantibody to nuclear antigens (ANA): use of reference sera of defined antibody specificity.

Standardization of the indirect immunofluorescence antinuclear antibody (IF-ANA) test can be improved for a given substrate with use of reference ANA sera, uniform assay conditions, and standardization of optical systems. To accomplish this, reference sera from the Arthritis Foundation with defined antibody specificities for nDNA, SS-B, RNP, Sm, nucleoli, and "speckled pattern" were reacted with commonly used IF-ANA substrates, mouse kidney sections, KB and HEp-2 tissue culture cells. Reagents and assay conditions used were those provided with the substrates in commercially available IF-ANA kits. A microscope slide with graded intensities of fluorescent beads was used to standardize microscope fluorescence intensity readings. The authors' fluorescence pattern and intensity results should be directly comparable to results obtained in other laboratories for the six antibodies for which reference sera are available. Although no defined sera are widely available for SS-A, Scl-70, PM-1, and centromere antibodies, the ability of each substrate to detect these antinuclear antibodies as well as mitochondrial, smooth muscle, ribosomal and microsomal antibodies also was tested. HEp-2 cells and KB cells were found to be superior to mouse kidney sections for detection of SS-A, Scl-70, PM-1 and centromere antinuclear antibodies. Mouse kidney sections were superior for screening of sera for the absence of ANA as well as for detection of smooth muscle and liver-kidney microsomal antibodies. Other antibodies were detected with equal sensitivity with all substrates and each of the three ANA kits used in the study performed satisfactorily. Use of reference sera as well as optical standardization is recommended for IF-ANA testing.

Animals↗
PubMed1984

Fibrin(ogen)olysis in polymyalgia rheumatica and temporal arteritis: preliminary findings on association with disease activity.

Postulating an increased production of fibrin(ogen)olytic degradation products (FDP) and an abnormality of fibrinogen metabolism in polymyalgia rheumatica (PMR) and temporal arteritis (TA), we studied 16 PMR/TA patients and 10 control subjects using a sensitive radioimmunoassay for a specific type of FDP, namely, fibrin(ogen)-related D-antigen. Median serum D-antigen levels were increased five-fold in those 11 PMR/TA patients who were untreated compared with control subjects. In the five PMR/TA patients who were treated with prednisone the median D-antigen levels were not significantly different from those of the healthy controls. D-antigen concentration correlated significantly (r = 0.83) with ESR in the seven untreated PMR patients. In PMR patients prednisone therapy was followed by a reduction of serum D-antigen levels.

Aged↗
PubMed1984

Proliferating cell nuclear antigen in blast crisis cells of patients with chronic myeloid leukemia.

A nuclear antigen associated with cell proliferation [proliferating cell nuclear antigen (PCNA)] and blast transformation is recognized by autoantibodies in the sera of some patients with systemic lupus erythematosus; these autoantibodies are precipitating antibodies and also react in immunofluorescence, a technique that was used to determine if PCNA might be expressed in leukocytes of patients with chronic myeloid leukemia (CML) during certain phases of their disease. At all times, a strong relationship was seen between the percentage of cells stained by anti-PCNA antibody and the percentage of blast cells in peripheral blood leukocytes (r) = 0.865, P less than .001. However, during blast crisis, certain cells that morphologically looked like myelocytes, metamyelocytes, and some cells with segmented nuclei stained with anti-PCNA serum. This staining, which remained nuclear in location, was less intense than in blast cells, suggesting low density of the antigen in these nonblast cells. This phenomenon was not observed in myelocytes or metamyelocytes obtained from patients in remission. These initial studies demonstrated that anti-PCNA can be used as a reagent to detect blast cells in CML crisis and also has the capability to detect PCNA in other cells associated with blast crisis.

Antigen-Antibody Complex↗