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Biomedical subjects

H Y Wu

Publications and source records attributed to H Y Wu.

At least 19 recordsLinked to original sources
PubMed1995

Long-range interaction between two promoters: activation of the leu-500 promoter by a distant upstream promoter.

The leu-500 mutation can be suppressed in S. typhimurium topA. Previous studies have demonstrated that the plasmid-borne leu-500 minimal promoter cannot be activated in topA mutants unless adjacent (< 250 bp) transcription occurs away from the leu-500 promoter (short-range promoter interaction). To search for a potential upstream promoter responsible for activation of leu-500 in the chromosomal context, we have identified the ilvlH promoter, located 1.9 kb upstream of leu-500 (long-range promoter interaction). Different from short-range promoter interaction, which is abolished by DNA sequence insertions, the long-range promoter interaction is mediated by the intervening DNA sequence. These studies suggest that the long-range interaction between a pair of divergently arrayed promoters is probably mediated by a complex process involving relay of DNA supercoiling by the DNA sequence located between the two promoters.

Base Sequence↗
PubMed1995

A nuclear suppressor overcomes defects in the synthesis of the chloroplast psbD gene product caused by mutations in two distinct nuclear genes of Chlamydomonas.

Mutations in two distinct nuclear genes, called NAC 1 and AC-115, of the unicellular green alga Chlamydomonas reinhardtii cause a specific and dramatic reduction in the synthesis of the chloroplast-encoded D2 polypeptide of Photosystem II. The psbD transcript which encodes the D2 protein is present in the mutant strains, but protein pulse-labeling and immunoprecipitation experiments demonstrate that the synthesis of the D2 protein does not occur normally in these cells. These phenotypes are suppressed by an extragenic nuclear suppressor isolated from a pseudorevertant of a nac 1 mutant. This suppressor is neither allele- nor gene-specific in its suppression and is able to overcome the effects of two different mutations in the NAC 1 gene, as well as a mutation in AC-115. The suppressor seems to be specific in its ability to remedy blocks in psbD mRNA translation in the chloroplast. It is not able to restore the translation of another chloroplast-encoded mRNA which is blocked by another nuclear mutation. The suppressor may identify a new nuclear gene specifically involved in the synthesis of the D2 protein in the chloroplast.

Animals↗
PubMed1995

The somatic hypermutation activity of a follicular lymphoma links to large insertions and deletions of immunoglobulin genes.

A biopsy specimen from a patient with follicular lymphoma was divided into two fragments. DNA was extracted from one fragment and a 1.2 kb region of the functional heavy chain (IgH) gene was amplified, cloned and sequenced (eight clones). From the other fragment a cell line (HF-1) was started. The IgH gene region was amplified from the cell line, and sequenced without cloning. The nine sequences obtained could be arranged into a genealogical tree where the individual sequences differed from the deduced ancestor by 16-29 single nucleotide changes, some also by an insertion and/or a deletion. It is apparent that the sequence alterations were caused by somatic mutations during the growth of the lymphoma. The comparison of the sequences with two published (allelic) germline sequences of the human JH region showed approximately 20% non-homology. The differences included five additional multinucleotide insertion/deletion changes, the longest of them a 101-nucleotide insertion. Two long insertions were homologous to the adjacent germline sequences. We propose that most of the changes observed, including long deletions and insertions, represent or are linked to somatic hypermutation events of the Ig gene type. Although in a few cases large deletions and insertions (> 2 bp) have been found in mutated immunoglobulin genes, our results, for the first time, firmly link these deletions/insertions to somatic hypermutations; their frequency was found to be 2.2% of the observed mutational events in the non-translated gene regions. HF-1 is the first follicular lymphoma line successfully established from a lymphoma known to have hypermutated its Ig genes during the malignant growth. It is a candidate cell line to be studied for its ability to generate mutations of B cell type in cell cultures.

Base Sequence↗
PubMed1995

[Selenium deficiency and thyroid hormone metabolism and function].

Type I 5'-deiodinase is a Se-containing enzyme. If Se is deficient, the deiodinase activity would be inhibited, the level of circulation T4 will be elevated, and the concentration T3 in peripheral tissues will be decreased. Se deficiency will also accelerate the iodine depletion of thyroid and may even exacerbate some detrimental effects of iodine deficiency. Possibly Se deficiency is involved in the occurrence and development of iodine deficient disorders. Keshan disease, with Se deficiency as the major cause, was also observed a change of thyroid hormone metabolism. The change of respiratory enzyme activities in myocardium of Keshan disease is in the way somewhat like that of hypothyroidism caused by iodine deficiency. The metabolic change of thyroid hormone after Se deficiency or iodine deficiency may be related to the occurrence of Keshan disease.

Animals↗
PubMed1992

Interlocking of plasmid DNAs due to Lac repressor-operator interaction.

The presence of a single lac repressor binding sequence on plasmid DNAs is shown to mediate the formation of interlocked dimers in E. coli. The presence of both homo- and hetero-interlocked dimers suggests that the lac repressor complex can bring together randomly two plasmid DNA molecules to facilitate gyrase-mediated interlocking. The exclusive formation of multiply intertwined dimers also suggest that the lac repressor complex may bind simultaneously to a pair of replicated daughter plasmid molecules prior to their segregation. The formation of interlocked plasmid DNAs can be indicative of interaction between two DNA bound proteins in vivo.

Base Sequence↗
PubMed1992

Identification of a DNA supercoiling activity in Saccharomyces cerevisiae.

A relaxed plasmid DNA is shown to become positively supercoiled in cell extracts from top1 strains of Saccharomyces cerevisiae. This positive supercoiling activity is dependent on the presence of bacterial DNA topoisomerase I and ATP (or dATP), and the positive supercoils generated in this reaction are not constrained by protein(s). Non-hydrolyzable ATP analogs cannot substitute for ATP in this supercoiling reaction, and the supercoiling activity is not due to RNA synthesis. The presence of an ARS sequence in the DNA does not alter the activity. Furthermore, this activity is equally active against UV irradiated or intact DNA. Extracts prepared from rad50 and rad52 mutant cells exhibited the same activity. Partial purification of this activity suggests that a protein factor with a native molecular weight of approximately 150 kDa is primarily responsible for the activity. The possibility that this supercoiling activity may be due to tracking of a protein along the intact duplex DNA is discussed.

Adenosine Triphosphate↗
PubMed1992

The structure of the Mental Health Inventory among Chinese in Taiwan.

This study attempted to ascertain the construct validity and external validity of the Mental Health Inventory in a Chinese population in Taiwan and contrast these results with results obtained from studies of several U.S. populations. In particular, a series of measurement models were specified and evaluated to address the issues of reliability and validity. Data were collected from personal interviews of a probability sample of 1,194 Chinese respondents 14 years of age and older in four townships in southwest Taiwan. The Mental Health Inventory was found to involve two major components: positive well-being and psychological distress. As a hierarchical structure, each component consists of one second-order and two or three first-order factors. The relationships between well-being and distress can be characterized as substantially independent and modestly bipolar depending on the level and specification.

Adolescent↗
PubMed1992

Serum antibody responses to Streptococcus mutans antigens in humans systemically infected with oral streptococci.

Sera from patients with subacute bacterial endocarditis (SBE) due to Streptococcus mutans or other oral streptococci and from normal subjects were assayed by enzyme-linked immunosorbent assay for antibodies to defined S. mutans antigens. Antibodies of IgG and IgA isotypes to Ag I/II and Ag III were greatly elevated in S. mutans-SBE sera, and the IgA antibodies in 3 sera included both polymeric and monomeric forms. Elevated IgM and IgG anti-lipoteichoic acid and IgG and IgA anti-serotype c polysaccharide antibodies were also found. The sera of 4 of 6 patients infected with other oral streptococci also displayed antibodies to S. mutans Ag I/II. Sera of 3 patients infected with Streptococcus mitis or Streptococcus oralis, but none of the S. mutans-infected cases, showed elevated antibodies to human heart sarcolemma, and all SBE sera had elevated rheumatoid factor. These results suggest that the known surface protein antigens of S. mutans are immunodominant in humans, and are not likely to be heart cross-reactive.

Antibodies, Bacterial↗
PubMed1992

Antibody-secreting cell responses in the mouse liver.

To elucidate the origins of biliary IgA antibodies, we investigated the isotype and specificity of antibody-secreting cells (ASC) in the liver in comparison with the spleen and intestinal lamina propria of mice immunized by peroral or parenteral routes. The profile of specific IgM, IgG1, IgG2a, and IgA ASC in the liver resembled that of the spleen rather than the lamina propria, regardless of the route of immunization. Peroral immunization increased the proportion of specific IgA ASC in all three organs. However, liver mononuclear cells (MNC) contained a higher proportion of total IgA-secreting cells than spleen cells. After immunization, the number and proportion of B220+ B cells were increased in the liver but not in the spleen. Although the predominant isotype of Ig and specific antibody in bile in response to immunization by either route was IgA, IgM and IgG were clearly detectable. However, specific activities of biliary antibodies relative to total Ig isotype were generally higher than in serum. The predominance of IgA-secreting cells in the liver and the large amount of IgA secreted in the bile resemble the situation at other secretory sites of the mucosal immune system. However, specific antibody-secreting cells appear to accumulate in the liver promptly after immunization, regardless of isotype, and contribute locally produced antibodies to the bile.

Administration, Oral↗
PubMed1991

DNA looping alters local DNA conformation during transcription.

The effect of protein-mediated DNA looping on local DNA conformation during active transcription was studied using the lac repressor-operator system. Our results suggest that lac repressor-mediated DNA looping within a plasmid DNA molecule containing two lac repressor binding sequences in vivo effectively separates plasmid DNA into two topological domains. Supercoils generated by transcription within each topological domain can be rapidly removed by DNA topoisomerase I.

Base Sequence↗
PubMed1991

Evidence in favor of the mechanical (intrauterine torsion) theory over the endocrinopathy (cryptorchidism) theory in the pathogenesis of testicular agenesis.

There are 2 competing theories regarding the pathogenesis of testicular agenesis--the endocrinopathy/cryptorchidism and the mechanical/intrauterine torsion theories. We compare the number of Leydig cells, total number of germ cells and the transformation of adult dark spermatogonia into primary spermatocytes in semithin sections of testicular biopsies from 59 contralateral descended testes of patients with testicular agenesis with those in the contralateral descended testes from 250 patients with unilateral cryptorchidism. The contralateral descended testes from boys with testicular agenesis demonstrated higher numbers of Leydig cells, higher numbers of total germ cells and a higher rate of transformation of adult dark spermatogonia into primary spermatocytes than did the contralateral descended testes from the patients with unilateral cryptorchidism. These findings favor the mechanical/intrauterine torsion theory over the endocrinopathy/cryptorchidism theory in the pathogenesis of testicular agenesis.

Biopsy↗
PubMed1991

Distribution, persistence, and recall of serum and salivary antibody responses to peroral immunization with protein antigen I/II of Streptococcus mutans coupled to the cholera toxin B subunit.

After peroral immunization of mice with surface protein antigen (Ag) I/II of Streptococcus mutans conjugated to the cholera toxin B (CTB) subunit, cells actively secreting immunoglobulin A (IgA) antibodies specific for Ag I/II, but not for CT, were induced in the salivary glands; salivary IgA anti-Ag I/II antibodies and total salivary IgA were also elevated. The development of large numbers of IgA and IgG antibody-secreting cells in the mesenteric lymph nodes and spleen and high levels of serum IgA and IgG antibodies to Ag I/II and CT demonstrated that a response to both antigens occurred. At least two to three intragastric doses of 15 micrograms or more of Ag I/II-CTB conjugate, plus free CT as an adjuvant, were needed to induce the salivary IgA anti-Ag I/II response, which peaked at about 35 days and persisted at lower levels for 5 to 6 months. A single booster intragastric immunization did not induce enhanced salivary IgA anti-Ag I/II antibodies relative to the primary response, but serum IgA and IgG antibodies to both Ag I/II and CT showed evidence of marked anamnestic responses. The results indicated that relatively long-term mucosal IgA antibody responses could be induced by peroral immunization with small quantities of a CTB-conjugated protein. However, additional factors governed the distribution of cells secreting antibodies of different specificities, or capable of mounting anamnestic responses, between different compartments of the mucosal and circulatory immune systems.

Adjuvants, Immunologic↗
PubMed1991

Role of nitrosamides in the high risk for gastric cancer in China.

Gastric cancer is the leading cause of death from cancer in China. Samples of fish sauce, a traditional seasoning, were collected in the high-risk area for gastric cancer in the Fuzhou area, Fujian Province. When fish sauce samples were nitrosated at pH 2.0, direct mutagenicity and high contents of N-nitrosamide were detected (30.9-78.0 microM); the N-nitrosamide content of three samples of fish sauce made in Guangdong and purchased from a market outside Fujian were low (2.1-6.0 microns). When the nitrosated fish sauce extract was given to newborn rats by gavage, dysplasia and adenocarcinoma were induced in the glandular stomach in the 4th and 16th experimental week, respectively. N-Nitrosamides were also found in fasting gastric juice from patients with chronic gastritis in the high-risk area of Putian. The mean concentration of total N-nitrosamides in the extracts correlated with the severity of gastritis in the stomach. These findings indicate that N-nitrosamides may play an important role in causing gastric cancer in China.

Animals↗