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M Y Lim

Publications and source records attributed to M Y Lim.

17 recordsLinked to original sources
PubMed2004

An in vitro comparison of the bleaching efficacy of 35% carbamide peroxide with established intracoronal bleaching agents.

AIM: To evaluate the bleaching efficacy of 35% carbamide peroxide, 35% hydrogen peroxide and sodium perborate for intracoronal bleaching of root filled discoloured teeth. METHODOLOGY: Extracted premolars were artificially stained using whole blood then root canal treatment was performed. After obturation, a 2 mm intermediate base was placed 1 mm below the buccal amelo-cemental junction. Intracoronal bleaching was performed in 11 teeth per group, using either 35% carbamide peroxide gel (group CP), 35% hydrogen peroxide gel (group HP) or sodium perborate mixed with distilled water (group SP). The bleaching agents were replaced after 7 days. The shade of the teeth was evaluated at day 0, 7 and 14. The results were analysed using Kruskal-Wallis one-way analysis of variance and Mann-Whitney U-test. RESULTS: At the end of 7 days, both groups CP and HP lightened by 8 +/- 3 Vita tab positions, respectively, whereas group SP lightened by 5 +/- 3 tab positions (P < 0.05). At the end of the second bleaching period at day 14, group CP and HP lightened by a further 2 +/- 2 and 2 +/- 3 tab positions, respectively, whereas group SP lightened by a further 3 +/- 4 tab positions. There were no statistical differences between groups at day 14. CONCLUSIONS: Thirty-five per cent carbamide peroxide and 35% hydrogen peroxide were equally effective for intracoronal bleaching, and significantly better than sodium perborate after 7 days. After 14 days, there were no significant differences between the groups. Thirty-five per cent carbamide peroxide can be recommended as an equally effective alternative to hydrogen peroxide for intracoronal bleaching.

Adolescent↗
PubMed2001

Light- and electron-microscopic analysis of neuropeptide Y-immunoreactive amacrine cells in the guinea pig retina.

We investigated the morphology and synaptic connections of neuropeptide Y (NPY)-containing neurons in the guinea pig retina by immunocytochemistry, using antisera against NPY. Specific NPY immunoreactivity was localized to a population of wide-field and regularly spaced amacrine cells with processes ramifying mainly in stratum 1 of the inner plexiform layer (IPL). Double-label immunohistochemistry demonstrated that all NPY-immunoreactive cells possessed glutamic acid decarboxylase 65 immunoreactivity. The synaptic connectivity of NPY-immunoreactive amacrine cells was identified in the IPL by electron microscopy. The NPY-labeled amacrine cell processes received synaptic input from other amacrine cell processes and bipolar cell axon terminals in stratum 1 of the IPL. The most frequent postsynaptic targets of NPY-immunoreactive amacrine cells were other amacrine cell processes. Synaptic outputs to bipolar cells were also observed in a small number of cases. This finding suggests that NPY-containing amacrine cells may influence inner retinal circuitry in stratum 1 of the IPL, thus mediating visual processing.

Amacrine Cells↗
PubMed1999

The pattern of lymphoma in east Malaysian patients as experienced in the University Hospital, Kuala Lumpur.

Lymphoma is a highly heterogeneous group of malignant disease. This study aimed to elucidate the pattern of lymphoma in the East Malaysian patient population. 107 cases of confirmed lymphomas from East Malaysian biopsy material were retrieved from the files of the Department of Pathology, University of Malaya, in the 3-year period between 1981 to 1983. With the use of a panel of lymphoid antibodies, the disease was sub-classified using the Rye classification for Hodgkin's lymphoma (HL) and the REAL classification for non-Hodgkin's lymphoma (NHL). All of the cases were tested for the presence of the Epstein-Barr virus by EBER-ISH. There were 11 (10.3%) HL, 80 (74.7%) B-NHL and 16 (15%) T-NHL. The HL:NHL ratio was 1:9. The most common tumour in children was Burkitt's lymphoma 7/13 (53.8%). In the adult group, there were 72/94 (76.6%) B-NHL ¿diffuse large cell type 51 (of which 2 were CD30+), Burkitt's lymphoma 8, follicular lymphoma 5, low grade MALT 2, mantle cell type 1 and not otherwise specified due to poor morphology 5¿, 13/94 (13.8%) T-NHL and 9/94 (9.6%) HL. Of the 9 adult HL, the most common subtype was nodular sclerosis (6, 66.7%). The EBER positive rate in classical HL, T-NHL, BL and B-NHL were 33.3%, 56.3%, 60.0% and 3.1% respectively. In conclusion, the spectrum of lymphoma seen in East Malaysia was rather similar to West Malaysia except for the very low prevalence of peripheral T-cell lymphoma (PTCL) in Sarawak (3.3%).

Adolescent↗
PubMed1998

Characterization of a Helicobacter pylori vaccine candidate by proteome techniques.

In a previous two-dimensional (2D) gel electrophoretic study of protein antigens of the gastric pathogen, Helicobacter pylori recognized by human sera, one of the highly and consistently reactive antigens, a protein with Mr of approximately 30,000 (Spot 15) seemed to be of special interest because of low yields on N-terminal protein sequencing. This suggested possible N-terminal modification, as the N-terminal sequence analysis of this 30,000 protein (Spot 15) did not provide a definitive match within the H. pylori genomic database. This protein was isolated by 2D polyacrylamide gel electrophoresis, evaluated by liquid chromatography-mass spectrometry, and found to consist of two related species of approximately 28,100 and 26,500. In parallel, the proteins within this spot were digested in situ with the endoprotease Lys-C. Analysis of the Lys-C digest by matrix-assisted laser desorption time-of-flight mass spectrometry, peptide mapping, and sequence analysis was conducted. Comparison of the mass and sequence of the Lys-C peptides with those derived from a H. pylori genomic library identified an open reading frame of approximately 300 base pairs as the source of the Spot 15 protein. This corresponded to HP0175 in the recently reported H. pylori genome sequence, an open reading frame with some homology to Campylobacter jejeuni cell binding protein 2. Mass spectral and sequence analysis indicated that Spot 15 was a processed product generated by proteolytic cleavage at both the carboxy and amino termini of the 34 open reading frame precursor.

Amino Acid Sequence↗
PubMed1998

Identification of potential diagnostic and vaccine candidates of Helicobacter pylori by two-dimensional gel electrophoresis, sequence analysis, and serum profiling.

There is great interest in characterizing the proteins of the gastric pathogen Helicobacter pylori, especially those to which humans respond immunologically, because of the potential importance of such proteins in diagnosis and vaccine development. Two-dimensional gel electrophoresis was used to separate and identify potential antigens of H. pylori ATCC 43504. Over 30 proteins were reactive in Western blots with pooled sera from 14 infected patients. These proteins were analyzed by N-terminal sequence analysis. Fourteen proteins were determined to be distinct from any proteins previously described from H. pylori; the others were previously isolated and characterized proteins. Analysis of eight distinct H. pylori strains showed that most of these antigens were produced by all of the strains. We propose that collection of new antigens such as those recognized here will be useful in serologic tests for detecting and monitoring H. pylori infection and may also serve as potential targets for antimicrobial agent or vaccine development.

Amino Acid Sequence↗
PubMed1997

Sequence variation and phylogenetic analysis of envelope glycoprotein of hepatitis G virus.

A transfusion-transmissible agent provisionally designated hepatitis G virus (HGV) was recently identified. In this study, we examined the variability of the HGV genome by analysing sequences in the putative envelope region from 72 isolates obtained from diverse geographical sources. The 1561 nucleotide sequence of the E1/E2/NS2a region of HGV was determined from 12 isolates, and compared with three published sequences. The most variability was observed in 400 nucleotides at the N terminus of E2. We next analysed this 400 nucleotide envelope variable region (EV) from an additional 60 HGV isolates. This sequence varied considerably among the 75 isolates, with overall identity ranging from 79.3% to 99.5% at the nucleotide level, and from 83.5% to 100% at the amino acid level. However, hypervariable regions were not identified. Phylogenetic analyses indicated that the 75 HGV isolates belong to a single genotype. A single-tier distribution of evolutionary distances was observed among the 15 E1/E2/NS2a sequences and the 75 EV sequences. In contrast, 11 isolates of HCV were analysed and showed a three-tiered distribution, representing genotypes, subtypes, and isolates. The 75 isolates of HGV fell into four clusters on the phylogenetic tree. Tight geographical clustering was observed among the HGV isolates from Japan and Korea.

Amino Acid Sequence↗
PubMed1995

Overexpression of the yeast MCK1 protein kinase suppresses conditional mutations in centromere-binding protein genes CBF2 and CBF5.

We find that overexpression in yeast of the yeast MCK1 gene, which encodes a meiosis and centromere regulatory kinase, suppresses the temperature-sensitive phenotype of certain mutations in essential centromere binding protein genes CBF2 and CBF5. Since Mck1p is a known serine/threonine protein kinase, this suppression is postulated to be due to Mck1p-catalyzed in vivo phosphorylation of centromere binding proteins. Evidence in support of this model was provided by the finding that purified Mck1p phosphorylates in vitro the 110 kDa subunit (Cbf2p) of the multimeric centromere binding factor CBF3. This phosphorylation occurs on both serine and threonine residues in Cbf2p.

Fungal Proteins↗
PubMed1993

Yeast MCK1 protein kinase autophosphorylates at tyrosine and serine but phosphorylates exogenous substrates at serine and threonine.

The product of the Saccharomyces cerevisiae MCK1 gene is a protein kinase that phosphorylates poly (Glu,Tyr) in vitro and is itself phosphorylated at both tyrosine and serine in vivo. To characterize the substrate specificity of Mck1, the enzyme was purified to apparent homogeneity from the soluble fraction of yeast cell extracts by ammonium sulfate precipitation, followed by ion exchange chromatography (Q- and S-Sepharose), dye-ligand affinity chromatography (Orange A-agarose), adsorption chromatography (hydroxylapatite), and ion exchange fast protein liquid chromatography (Mono-S). In the absence of an exogenous substrate, purified Mck1 was able to autophosphorylate on tyrosine and serine. A catalytically inactive mutant (K68R in conserved kinase domain II) expressed in an mck1 delta strain did not contain detectable phosphotyrosine, confirming that the tyrosine phosphorylation observed in vivo is due to autophosphorylation, but did contain phosphoserine, suggesting that Mck1 is a target for other cellular protein kinases. Purified Mck1 phosphorylated a variety of proteins in heat-inactivated yeast extracts, primarily on serine (and threonine). The purified enzyme also used a number of mammalian proteins as phosphoacceptors, including myelin basic protein (MBP), microtubule-associated protein 2 (MAP-2), and tau protein. All of these substrates were phosphorylated on either serine or threonine (or both). Mck1 isolated from yeast extracts by immunoprecipitation with an anti-Mck1 antibody directed against its C terminus also phosphorylated MBP at serine. In the same immune complex kinase assay, the K68R mutant did not detectably phosphorylate MBP, indicating that the serine-specific phosphotransferase activity of Mck1 is intrinsic and not due to contamination by an associated kinase. These findings demonstrate that Mck1 is a member of a novel class of protein kinases that displays the ability to phosphorylate all three hydroxyamino acids in proteins.

Chromatography, Liquid↗
PubMed1990

The v-rel oncogene product is complexed with cellular proteins including its proto-oncogene product and heat shock protein 70.

The oncogene product, pp59v-rel, of avian reticuloendotheliosis virus (REV-T) is complexed in the cytosol of REV-T transformed lymphoid cells with cellular proteins. Monoclonal antibodies and antisera directed against different regions of pp59v-rel coimmunoprecipitate five cellular proteins (p124, p115, p75, p70, and p40) in addition to pp59v-rel. Cellular proteins with the same apparent molecular mass also copurify with pp59v-rel during sequential Sephacryl S200 and immunoaffinity chromatography. Antisera directed against the most abundant cellular protein in the complex, pp40, coimmunoprecipitate pp59v-rel and several cellular proteins with the same apparent molecular mass. The 75-kDa protein in the pp59v-rel complex is the product of c-rel proto-oncogene and is weakly phosphorylated. In MSB-1 cells this protein is not detectably phosphorylated or associated with cellular proteins. The 70-kDa protein in the pp59v-rel containing cytosolic complex is the constitutive form of avian heat shock protein 70 (HSC70). The p70 protein coimmunoprecipitates and copurifies with pp59v-rel using antisera directed against pp59v-rel and coimmunoprecipitates with antisera specific for pp40. The p70 isolated from immune complexes containing pp59v-rel shares V8 protease fragments with HSC70.

Animals↗
PubMed1990

Avian reticuloendotheliosis virus-transformed lymphoid cells contain multiple pp59v-rel complexes.

The v-rel oncogene of avian reticuloendotheliosis virus type T (REV-T) encodes a 59-kilodalton (kDa) phosphoprotein located principally in the cytosol of transformed lymphoid cells. All of the detectable pp59v-rel was present in high-molecular-weight complexes containing at least five cellular proteins (p124, p115, p75c-rel, p70hsc, and pp40). Antiserum was developed against the 40-kDa protein, the most abundant cellular protein associated with the complex. The 40-kDa phosphoprotein was complexed with pp59v-rel in REV-T-transformed lymphoid cell lines arrested at different stages of B-cell development as well as in lymphoid tumor cells and in fibrosarcomas. The half-life (8 h) of pp40 in REV-T-transformed lymphoid cells was the same as that of pp59v-rel. Antiserum against pp40 permitted the identification of two pp59v-rel complexes. The most abundant cytoplasmic complex contained approximately 75% of the pp59v-rel and all of the detectable pp40 in REV-T-transformed lymphoid cells. Twenty-five percent of the pp59v-rel was present in a minor complex that contained the majority of p75c-rel along with p115 and p124. In nuclear extracts of REV-T-transformed lymphoid cells, pp59v-rel was complexed with pp40. The two high-molecular-weight proteins (p115 and p124) and p75c-rel were not detected in the nuclear complex. In the cytosolic complexes, pp40 was heavily phosphorylated, whereas the nuclear form was much less extensively phosphorylated.

Animals↗
PubMed1990

Novel yeast protein kinase (YPK1 gene product) is a 40-kilodalton phosphotyrosyl protein associated with protein-tyrosine kinase activity.

Extracts of bakers' yeast (Saccharomyces cerevisiae) contain protein-tyrosine kinase activity that can be detected with a synthetic Glu-Tyr copolymer as substrate (G. Schieven, J. Thorner, and G.S. Martin, Science 231:390-393, 1986). By using this assay in conjunction with ion-exchange and affinity chromatography, a soluble tyrosine kinase activity was purified over 8,000-fold from yeast extracts. The purified activity did not utilize typical substrates for mammalian protein-tyrosine kinases (enolase, casein, and histones). The level of tyrosine kinase activity at all steps of each preparation correlated with the content of a 40-kDa protein (p40). Upon incubation of the most highly purified fractions with Mn-ATP or Mg-ATP, p40 was the only protein phosphorylated on tyrosine. Immunoblotting of purified p40 or total yeast extracts with antiphosphotyrosine antibodies and phosphoamino acid analysis of 32P-labeled yeast proteins fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the 40-kDa protein is normally phosphorylated at tyrosine in vivo. 32P-labeled p40 immunoprecipitated from extracts of metabolically labeled cells by affinity-purified anti-p40 antibodies contained both phosphoserine and phosphotyrosine. The gene encoding p40 (YPK1) was cloned from a yeast genomic library by using oligonucleotide probes designed on the basis of the sequence of purified peptides. As deduced from the nucleotide sequence of YPK1, p40 is homologous to known protein kinases, with features that resemble known protein-serine kinases more than known protein-tyrosine kinases. Thus, p40 is a protein kinase which is phosphorylated in vivo and in vitro at both tyrosine and serine residues; it may be a novel type of autophosphorylating tyrosine kinase, a bifunctional (serine/tyrosine-specific) protein kinase, or a serine kinase that is a substrate for an associated tyrosine kinase.

Amino Acid Sequence↗
PubMed1988

Rearrangements of chicken immunoglobulin genes in lymphoid cells transformed by the avian retroviral oncogene v-rel.

The retroviral oncogene v-rel transforms poorly characterized lymphoid cells. We have explored the nature of these cells by analyzing the configuration and expression of immunoglobulin genes in chicken hemopoietic cells transformed by v-rel. None of the transformed cells expressed their immunoglobulin genes. The cells fell into three classes: class I cells have their immunoglobulin genes potentially in an embryonic configuration; class II and class III cells have lost one copy of the lambda light chain locus and have one copy of the heavy chain locus rearranged into a configuration that differs from what is found in mature B cells. In class II cells, the other heavy chain locus may be in embryonic configuration, whereas it is deleted in class III cells. The first of these classes may represent the earliest stage of the lymphoid lineage yet encountered among virus-transformed cells, whereas the second and third classes represent an apparently anomalous rearrangement whose origin remains unknown.

Animals↗
PubMed1988

The v-rel oncogene product is complexed to a 40-kDa phosphoprotein in transformed lymphoid cells.

The transforming protein encoded by the v-rel oncogene of avian reticuloendotheliosis virus (REV-T) is a very low copy number molecule in the cytosol of transformed cells. Analysis of cytosolic extracts from a REV-T-transformed lymphoid cell line by gel filtration on Sephacryl S-300 indicated that most of the v-rel oncogene product, pp59v-rel, eluted with an apparent molecular mass of 400 kDa. The size of this complex was confirmed by analysis on a fast-protein liquid chromatography gel filtration column. A 40-kDa cellular protein copurified with pp59v-rel on sequential gel filtration on Sephacryl S-200 and immunoaffinity chromatography with a monoclonal antibody directed against pp59v-rel. The 40-kDa cellular protein could also be immunoprecipitated together with pp59v-rel from cell extracts of [35S]methionine-labeled cells, suggesting that pp59v-rel is complexed with the 40-kDa protein in transformed lymphoid cells. Both the 59- and 40-kDa proteins were phosphorylated when the highly purified preparation containing pp59v-rel was incubated with [gamma-32P]ATP and 10 mM MgCl2 in vitro. The identity of the kinase in the highly purified preparation containing pp59v-rel, however, is unknown. Immune complexes recovered from extracts of REV-T-transformed lymphoid cells labeled with [32P]orthophosphate also contained the 59- and 40-kDa phosphoproteins. These observations suggest that pp59v-rel is complexed with a 40-kDa cellular phosphoprotein to form a 400-kDa heteropolymer in the cytoplasm of transformed lymphoid cells.

Animals↗
PubMed1987

The transforming protein of avian reticuloendotheliosis virus is a soluble cytoplasmic protein which is associated with a protein kinase activity.

We have identified the product (p57v-rel) of the transforming gene, v-rel, of avian reticuloendotheliosis virus (REV-T) using antisera generated against nonoverlapping sequences representing the middle and carboxy-terminal regions of the v-rel protein expressed in Escherichia coli (N.K. Herzog and H.R. Bose, Jr., 1986, Proc. Natl. Acad. Sci. USA 83, 812-816). The amino-terminal region of the v-rel protein was also expressed in E. coli and used to generate antisera. The immunoglobulin-enriched fractions of these antisera were used to determine the subcellular location of p57v-rel in REV-T transformed lymphoid cells. Cells were fractionated into nuclear, mitochondrial, microsomal, and cytoplasmic fractions. The majority of p57v-rel was found in the cytoplasm. Examination of REV-T transformed lymphoid cells labeled with 32Pi revealed that the majority of the phosphorylated form of the v-rel protein was also found in the cytoplasm. Indirect immunofluorescence of REV-T transformed cells gave a diffuse cytoplasmic pattern indicating that p57v-rel was not associated with any discrete cellular organelle. The distribution of p57v-rel was similar in REV-T transformed lymphoid cells labeled with [35S]methionine for short and long periods of time, suggesting that p57v-rel is a soluble cytoplasmic protein throughout its lifetime. The v-rel protein was phosphorylated when immune complexes precipitated from transformed cells with the immunoglobulin fractions obtained from antisera against the amino-terminal, middle, and carboxy-terminal regions of v-rel were incubated with [gamma-32P]ATP and Mn2+. The phosphorylation of p57v-rel in the in vitro immune complex kinase assay was inhibited when the immunoglobulin-enriched fraction of these antisera was preincubated with the homologous v-rel fusion proteins. Preincubation with heterologous proteins did not block the phosphorylation of p57v-rel. These observations suggest that p57v-rel is associated with a protein kinase activity. Most of the kinase activity was found in the soluble cytoplasmic fraction of transformed cells. The transforming protein encoded by v-rel is a relatively stable protein with a half-life of approximately 7 to 8 hr in transformed lymphoid cells.

Cell Transformation, Viral↗
PubMedDate not supplied

Enhanced dissolution of gallstone by combining ethanol with two commonly used cholelitholytic solvents.

BACKGROUND/AIMS: Contact dissolution therapy is one of the non-surgical treatments for patients with gallstone. Among the various solvents, methyl tert-butyl ether (MTBE) is used for cholesterol gallstone, while tetrasodium ethyl-dimethyl tetraacetate (EDTA-4Na) solution is used to dissolve calcium bilirubinate stones. However, the contents of gallstone cannot be precisely predicted while they are still present in the human body. This study was designed to test if the MTBE and EDTA can be mixed together and to test the solubility of different kinds of gallstone in each original solution and mixture. METHODOLOGY: Each 0.1 gm of mixed cholesterol stone, brown stone and pigment stone from 18 patients was used. Pure ethanol was chosen to enhance the miscibility between the organic phase of MTBE and the aqueous phase of EDTA. The contents of gallstone after dissolution were examined with scanning electromicroscopy. RESULTS: We found the mixture of ethanol, MTBE and EDTA to be the most efficient solvent in gallstone dissolution in comparison with the other two original solvents. The mixture reached a dissolution percentage of 97.96 +/- 1.00, 88.96 +/- 6.51 and 67.75 +/- 14.26 for cholesterol, brown and black pigment gallstone, respectively. CONCLUSIONS: We concluded that ethanol can be used to mix the MTBE and EDTA with good preservation in their litholytic effects on gallstone. The ethanol-MTBE-EDTA solvent is, therefore, a promising universal cholelitholytic agent which deserves further tests for its safety and efficacy in the in vivo study.

Cholagogues and Choleretics↗