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Biomedical subjects

M Y Liu

Publications and source records attributed to M Y Liu.

At least 73 records · Page 4Linked to original sources
PubMed1997

Primary infections of human herpesvirus-7 and herpesvirus-6: a comparative, longitudinal study up to 6 years of age.

In order to understand the infection status of human herpesvirus 7 (HHV-7) in Taiwan and clarify the serological cross-reactivity between HHV-7 and HHV-6, a longitudinal study was carried out in 52 infants from whom 9 sera were available from birth to 6 years of age. All sera were tested for antibodies against HHV-6 and HHV-7 by indirect immunofluorescence assay. HHV-7 infection was not seen before 6 months of age and gradually emerged thereafter, reaching a cumulative rate of 28.8%, 67.3%, 73.1%, 78.8%, 82.7%, and 86.5% by the ages of 1, 2, 3, 4, 5 and 6 years, respectively. Primary HHV-6 infection induced a reactive HHV-7 antibody in 10/28 (35.7%) cases with a titre of no more than 10. Twenty-eight children (53.8%) were infected by HHV-6 earlier than HHV-7, while eight (15.4%) were infected by HHV-7 earlier than HHV-6. In summary, HHV-7 infected children later than HHV-6. A one-way cross-reaction of HHV-7 serology by HHV-6 was revealed and a titre of 20 is appropriate for defining HHV-7 infection.

Adolescent↗
PubMed1997

The global regulator CsrA of Escherichia coli is a specific mRNA-binding protein.

The csrA gene encodes a global regulatory protein which facilitates glgC mRNA decay in vivo. A purified recombinant CsrA protein was found to inhibit in vitro glg (glycogen biosynthesis) gene expression posttranscriptionally and bind specifically to a glgC runoff transcript without causing its decay. Our results provide further insight into the mechanism by which CsrA functions as an mRNA decay factor.

Bacterial Proteins↗
PubMed1997

Molecular subtyping of human T-lymphotropic virus type I (HTLV-I) by a nested polymerase chain reaction-restriction fragment length polymorphism analysis of the envelope gene: two distinct lineages of HTLV-I in Taiwan.

The major type of human T-lymphotropic virus type I (HTLV-I), generally referred to as the cosmopolitan type, has been grouped into three subtypes (A, B, and C) by phylogenetic analysis of the long terminal repeat sequences of the viral genome. Twelve subtype-specific nucleotide variations have been deduced by comparison between the envelope (env) sequences of 16 HTLV-I strains with defined subtypes and 9 Taiwanese HTLV-I strains. To gain further insights into the molecular epidemiology of HTLV-I and the origin of this virus in Taiwan, a rapid method of identification for the cosmopolitan subtypes was developed by using a nested polymerase chain reaction (PCR) and subsequent restriction fragment length polymorphism (RFLP) studies using the two subtype B-specific and four subtype C-specific nucleotides located within the positions 5708 to 6320 of the envgene. The nested PCR-RFLP method was used to subtype HTLV-I from four virus-positive cell lines derived from 1 Japanese and 3 North American patients, as well as 41 blood-unrelated Taiwan Chinese. The sequences of PCR products were determined and the six positions of subtype-specific nucleotide variations were examined. The sequence data completely supported the subtyping data via the nested PCR-RFLP method. The results demonstrated that, as is the case in Japan, at least two distinct cosmopolitan subtypes (A and B) of HTLV-I were present in Taiwan, but the more prevalent subtype in Taiwan is A in contrast to subtype B in Japan. Furthermore, rapid subtyping could facilitate molecular epidemiological studies of HTLV-I infection and linkage between HTLV-I subtypes and virus-associated diseases.

Base Sequence↗
PubMed1997

Evaluation of multiple antibodies to Epstein-Barr virus as markers for detecting patients with nasopharyngeal carcinoma.

Five serological tests were assessed for their sensitivity for screening and early detection of nasopharyngeal carcinoma (NPC). The tests included the detection of antibodies to various gene products of EBV: viral capsid antigen (VCA) using an indirect immunofluorescence assay (FA), DNase using an activity neutralisation test (NT), Dnase using an enzyme-linked immunosorbent assay (ELISA), DNA polymerase (DP) using NT, and major DNA binding protein (MDBP) by ELISA. Sera from 100 NPC outpatients and 20 NPC patients, who were detected in a prospective study, were examined. The results showed that levels of antibody to DNase detected by ELISA and to DP detected by NT and the positivity rate for VCA by FA increased with NPC stage. More species of EBV antibody became detectable as NPC progressed. The detection of anti-MDBP antibody by ELISA was suitable for screening for NPC. Anti-DP antibody detected by NT was a valuable marker both for early detection and prognosis of NPC. Detection of anti-DNase antibody by ELISA was the most sensitive method for detection of NPC. No single test was sufficient to detect all the NPC patients and a combination of anti-DNase by ELISA with other tests are recommended to identify NPC patients.

Antibodies, Viral↗
PubMed1996

Identification of a BglI polymorphism of catechol-O-methyltransferase (COMT) gene, and association study with schizophrenia.

Several linkage studies suggested chromosome 22q11-13 may harbor susceptible genes for schizophrenia. Catechol-O-methyl-transferase (COMT), which is involved in the metabolism of catecholamines, was mapped to 22q11 and is considered a possible candidate gene for schizophrenia. Recently, we identified a polymorphic marker, a single nucleotide C insertion at the 3' untranslated region of the COMT gene, which obliterates a BglI site. Using this BglI polymorphism, we conducted a case-control association study in Chinese patients with schizophrenia. No significant differences of allele and genotype frequencies were noted between patients (N = 177) and controls (N = 99). When patients were subgrouped according to sex, no significant differences of genotype and allele frequencies were noted in either male or female patients compared to normal controls. Our results do not support an association between the BglI polymorphism of COMT gene and schizophrenia.

Catechol O-Methyltransferase↗
PubMed1996

A structure-based catalytic mechanism for the xanthine oxidase family of molybdenum enzymes.

The crystal structure of the xanthine oxidase-related molybdenum-iron protein aldehyde oxido-reductase from the sulfate reducing anaerobic Gram-negative bacterium Desulfovibrio gigas (Mop) was analyzed in its desulfo-, sulfo-, oxidized, reduced, and alcohol-bound forms at 1.8-A resolution. In the sulfo-form the molybdenum molybdopterin cytosine dinucleotide cofactor has a dithiolene-bound fac-[Mo, = O, = S, ---(OH2)] substructure. Bound inhibitory isopropanol in the inner compartment of the substrate binding tunnel is a model for the Michaelis complex of the reaction with aldehydes (H-C = O,-R). The reaction is proposed to proceed by transfer of the molybdenum-bound water molecule as OH- after proton transfer to Glu-869 to the carbonyl carbon of the substrate in concert with hydride transfer to the sulfido group to generate [MoIV, = O, -SH, ---(O-C = O, -R)). Dissociation of the carboxylic acid product may be facilitated by transient binding of Glu-869 to the molybdenum. The metal-bound water is replenished from a chain of internal water molecules. A second alcohol binding site in the spacious outer compartment may cause the strong substrate inhibition observed. This compartment is the putative binding site of large inhibitors of xanthine oxidase.

Aldehyde Oxidoreductases↗
PubMed1996

Involvement of Phe19 in the Mn(2+)-L-malate binding and the subunit interactions of pigeon liver malic enzyme.

A triple mutant, F19S/N250S/L353Q, of pigeon liver malic enzyme was found to have no detectable enzymatic activity [Chou, W.-Y., Huang, S.-M., & Chang, G.-G. (1994) Arch. Biochem. Biophys. 310, 158-166]. In the present study, point mutants at these positions (F19S, N250S, and L353Q) were prepared by site-directed mutagenesis. Both N250S and L353Q have kinetic properties similar to those of the wild-type. On the other hand, the K(m)(app) values for both Mn2+ and L-malate of F19S were increased by approximately 10-fold, while the kcat value was decreased by 5-fold, which results in a decrease of the apparent catalytic efficiency (kcat/K(mNADP)K(mMal)K(mMn) by approximately 300-fold. These results clearly indicate that the F19S mutation is mainly responsible for the undetectable enzyme activity of the triple mutant. Three more Phe19 mutants (F19Y, F19G, and F19A) were then prepared. There is a direct correlation between the size of the substitutes and the affinities for Mn2+ and L-malate. The kinetic parameters for F19Y were similar to those for wild-type. Both F19A and F19G reveal a 5-fold decrease of kcat values. Two K(dMn) values for the high- and low-affinity sites, respectively, were detectable for the wild-type. On the contrary, only one K(dMn) value was detected for the F19 mutants, which was increased in the order of F19G > F19A > F19S > F19Y, with F19G being the most affected mutant. The K(mMal) values of F19G and F19A were increased 100- and 6-fold, respectively. The catalytic efficiency (kcat/K(mNADP)K(dMal)K(dMn)) of F19G was decreased to only 0.01% of that of the wild-type. The above results clearly indicate that the hydrophobic aromatic ring at position 19 plays a critical role in L-malate and Mn2+ binding. Furthermore, all mutants that have a small residue at position 19 exist as monomers. Therefore, Phe19 may locate in or near the regions for Mn(2+)-L-malate binding as well as for the subunit contact. These results are compatible with the asymmetric model for the quaternary structure of malic enzyme we proposed previously [Chang, G.-G., Huang, T.-M., Huang, S.-M., & Chou, W.-Y. (1994) Eur. J. Biochem. 225, 1021-1027]. The possible roles of the N-terminus of malic enzyme were also addressed.

Amino Acid Sequence↗
PubMed1996

Cloning, characterization, and expression of the nitric oxide-generating nitrite reductase and of the blue copper protein genes of Achromobacter cycloclastes.

The nitrite reductase (NIR) and blue copper protein (BCP) genes have been cloned from Achromobacter cycloclastes and characterized. NIR gene encodes a protein of 378 amino acid residues including a putative signal peptide of 37 residues. BCP gene encodes a protein of 148 residues with a 24-residue signal peptide. The DNA-derived amino acid sequence of NIR is in complete agreement with that from Edman degradation and the DNA coding sequence of BCP is also consistent with its partial N-terminal amino acid sequence. Both genes contain their own FNR box in the 5' upstream region and a TA-rich region that could be the transcription start site. These two genes are separated by at least 10 kb. Based on these observations it is very likely that these two genes, although functionally related, are regulated independently. Both proteins could be expressed in E. coli, and both of the expressed proteins could be recognized by their respective antisera. The expressed NIR demonstrates full enzymatic activity. The similarity of both proteins to the counterparts from Alcaligenes faecalis S-6 is discussed.

Alcaligenes↗
PubMed1996

Genomic analysis of Epstein-Barr virus in nasal and peripheral T-cell lymphoma: a comparison with nasopharyngeal carcinoma in an endemic area.

The Epstein-Barr virus (EBV) is prevalent in nasal and peripheral T-cell lymphoma (NPTL) in Taiwan, where nasopharyngeal carcinoma (NPC) is endemic. In order to understand the pathogenesis of these two malignancies in this endemic area, genomic analysis of EBV in NPTL with comparison to NPC is important. We investigated the EBV subtype (types A and B), BamH-I "f" variant, and the Xho-I site mutant of the latent membrane protein-1 (LMP-1) gene in 19 cases of EBV-associated NPTL and in 30 cases of NPC. EBV DNA from three patients with infectious mononucleosis (IM) was simultaneously studied as representative of normal healthy carriers. Similar to NPC and IM, the EBV in NPTL was found to belong to the type A strain in the majority (18 of 19) of cases by analyzing the 3' divergence of EBNA-2 genes. The extra restriction enzyme site in the BamHI-F region ("f" variant) of EBV DNA was frequently (15 of 30) demonstrated in NPC, but only rarely (1 of 19) was it detected in NPTL and IM (0 of 3). The Xho-I site mutant of the LMP-1 gene previously characterized in Chinese NPC also prevailed in NPTL and IM with an identical nucleotide sequence. No correlation exists between the EBV subtype and its variants. In conclusion, type A EBV is prevalent in Taiwanese NPTL, a finding much distinct from the dominance of type B virus in nonendemic European patients. The EBV genomes in NPTL are closely similar to those in IM or normal healthy carriers, but are distinct from NPC for the infrequency of the "f" variant. The prevalence of the LMP-1 mutant in this endemic region suggests that this EBV strain may confer a growth advantage role in the pathogenesis of these EBV-associated diseases. The rarity of the "f" variant in NPTL and its high frequency in NPC may explain the differential tumorigenesis of different EBV strains.

Cloning, Molecular↗
PubMed1996

Pineal ganglioglioma with premature thelarche. Report of a case and review of the literature.

We report a case of a 6-year-old girl with a ganglioglioma in the pineal region presenting with a rare clinical picture of premature thelarche. Intracranial gangliogliomas are rare, especially in the pineal region. Their character, origin, treatment, and prognosis remain controversial. The pathophysiology of precocious puberty associated with pineal ganglioglioma is discussed.

Brain Neoplasms↗
PubMed1996

Functional analysis of C-terminal deletion mutants of Epstein-Barr virus thymidine kinase.

Thymidine kinase (TK) activity was detected following expression of the TK gene of Epstein-Barr virus (EBV) using the pET expression plasmid and E. coli BL21 (DE3)pLysS. To study the amino acid residues required at the C terminus of the EBV TK protein for enzymatic activity, a series of C-terminal deletion mutants was generated by direct truncation, linker insertion or PCR mutagenesis to create stop codons at particular sites. Deletion of nine residues from the C terminus caused a 35% reduction in TK activity, while a ten-residue deletion completely abolished the activity. A single point mutation at residue Cys570, corresponding to Cys336 of herpes simplex virus TK, did not alter the TK activity. Single amino acid changes within the last seven to ten residues also did not affect activity. The results indicate that maintenance of the conformation of the C terminus is important for enzyme activity.

Base Sequence↗
PubMed1996

Coordinate genetic regulation of glycogen catabolism and biosynthesis in Escherichia coli via the CsrA gene product.

The carbon storage regulator gene, csrA, encodes a factor which negatively modulates the expression of the glycogen biosynthetic gene glgC by enhancing the decay of its mRNA (M. Y. Liu, H. Yang, and T. Romeo, J. Bacteriol. 177:2663-2672, 1995). When endogenous glycogen levels in isogenic csrA+ and csrA::kanR strains were quantified during the growth curve, both the rate of glycogen accumulation during late exponential or early stationary phase and its subsequent rate of degradation were found to be greatly accelerated by the csrA::kanR mutation. The expression of the biosynthetic genes glgA (glycogen synthase) and glgS was observed to be negatively modulated via csrA. Thus, csrA is now known to control all of the known glycogen biosynthetic genes (glg), which are located in three different operons. Similarly, the expression of the degradative enzyme glycogen phosphorylase, which is encoded by glgY, was found to be negatively regulated via csrA in vivo. The in vitro transcription-translation of glgY was also specifically inhibited by the purified CsrA gene product. These results demonstrate that localization of glycogen biosynthetic and degradative genes within the Escherichia coli glgCAY operon facilitates their coordinate genetic regulation, as previously hypothesized (T. Romeo, A. Kumar, and J. Preiss, Gene 70:363-376, 1988). The csrA gene did not affect glycogen debranching enzyme, which is now shown to be encoded by the gene glgX.

Bacterial Proteins↗
PubMed1996

[Sequence analyses of Epstein-Barr virus (EBV) Bam HI F DNA fragment in EBV associated diseases].

In order to compare nucleotide differences of Epstein-Barr virus (EBV) Bam HI F DNA fragment from various EBV associated diseases, polymerase chain reactions (PCR) were used to amplify a subfragment (nucleotides 55,381-56,020) of the F fragment from different tissue DNAs, including 20 NPCs, 2 B-cell lymphomas, 2 T-cell lymphomas, 3 infectious mononucleosis (IM), and 3 normal controls. DNA sequences were determined by PCR direct sequencing or sequencing after DNA cloning. The PCR products were cloned into pGEM-3Z vector, then the resulting recombinant plasmids were used to transform DH5 alpha competent cells. Plasmid DNAs from the correct transformants were prepared for DNA sequencing. The results showed that the proportion of the f variant in NPCs, B-cell lymphomas, T-cell lymphomas, IMs, and normals were 40%, 0%, 0%, 33%, and 33%, respectively. Because the f variant was not specifically more prevalent in NPC tissues compared to the non-tumor tissues, we speculate that there is no strong association between the f variant and NPC. These results were different from other reports. Coinfection of the F strain and the f variant was found both in some NPC patients and normal individuals. Analyses of Bam HI F subfragments of 35 EBV isolates from the 30 tissue DNAs revealed that there were changes at four corresponding positions of the B95-8 strain. They were nucleotide T at 55,473 replaced by G, an insertion of TGT after nucleotide 55,543, nucleotide A at 55,564 replaced by G, and nucleotide T at 55,958 replaced by C. These 4 nucleotide changes may confer a character of Taiwan strains. The nucleotides of the F strain at coordinates 55,519, 55,596, 55,680, 55,703, and 55,895 were T, T, A, A, and C, and those for the f variant were C, C, C, C, and T. These two patterns were not correlated with types A and B of EBV.

Base Sequence↗
PubMed1996

Use of bacterially expressed GST/EBNA-1 fusion proteins for detection of antibodies in sera from patients with nasopharyngeal carcinoma and healthy donors.

Epstein-Barr virus nuclear antigen-1 (EBNA-1) is a protein expressed consistently in EBV infected cells and in EBV related malignant tissues. Antibodies against EBNA-1 may therefore possibly be used as a marker for disease screening. Western blot analysis of serum antibodies was performed using GST (glutathione-S-transferase) fusion proteins containing different regions of EBNA-1 as antigens. Serum samples were collected from 38 patients with nasopharyngeal carcinoma (NPC) and 38 healthy individuals in Taiwan. All samples were found IgG positive for EBNA-1 when a truncated protein GST/E1 (70-102, 325-641) was used as the antigen. Thirty-three out of 38 NPC sera (86.8%) were positive for IgA antibody against EBNA-1. The positive rate was higher in comparison with IgA antibody against VCA (65.7%) or antibody against DNase (60.5%). Only 2.6% of sera from normal individuals were positive for an IgA response against EBNA-1. The major antigenic determinants for NPC serum IgA response were between amino acid(aa) 390 to aa 459 when different portions of EBNA-1 were used as antigens. The results suggest that IgA response against EBNA-1 could be used in combination with other EBV serology markers for NPC screening.

Animals↗
PubMed1996

Screening of drugs inhibiting Epstein-Barr virus replication.

At the present moment, drugs which can inhibit Epstein-Barr virus replication are very rare, and their effects are not satisfactory. Therefore, it is necessary to develop new drugs to obtain a better treatment. Forty-one synthetic chemical compounds including purine analogs and nucleoside analogs were collected. These compounds were serially diluted and added to Akata cells, an EBV-containing cell line derived from Burkitt's lymphoma. The cells were immediately added with anti-human IgG to activate EBV replication within the cells. After one day of incubation, reduction of EBV protein synthesis was determined by indirect immunofluorescence assay and Western blotting. Inhibition of viral DNA replication was assayed by slot blot hybridization. The results showed that nucleoside analogs 2-methyl-5, 6-dichloro-1-(beta-D-ribofuranosyl) benzimidazole and 2-ethyl-5, 6-dichloro-1-(beta-D-ribofuranosyl) benzimidazole appeared to be the best drugs analyzed.

Antiviral Agents↗
PubMed1996

Mesial temporal dysembryoplastic neuroepithelial tumor mimicking oligodendroglioma: a case report and review of the literature.

Dysembryoplastic neuroepithelial tumor (DNT) is an uncommon congenital tumor occurring in children. We report a 12-year-old boy who had a focal motor seizure involving his left face 6 months prior to admission. Preoperative computed tomography of the brain demonstrated a focal calcified tumor measuring 2.5 cm in diameter in the right temporal lobe. Initial pathological diagnosis was oligodendroglioma, and postoperative radiotherapy with a total dose of 5000 cGy in 28 fractions over 5&1/2 weeks was given. At follow-up 8 months later, neither clinical nor radiological recurrence was found. Because of the benign clinical course, a review of the surgical specimen was made, which led to the diagnosis of DNT. It is important to distinguish DNT from other tumors that have a worse prognosis. Correct diagnosis may prevent unnecessary radiotherapy or chemotherapy. The pathologic and radiologic diagnostic criteria of DNT are discussed, with a review of the literature.

Brain Neoplasms↗