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Biomedical subjects

H Liang

Publications and source records attributed to H Liang.

At least 199 records · Page 11Linked to original sources
PubMed1994

Solution structure of the ets domain of Fli-1 when bound to DNA.

Members of the ets family of transcription factors share a conserved DNA-binding domain, the ets domain. By using multidimensional NMR, we have determined the structure of the ets domain of human Fli-1 in the DNA-bound form. It consists of three alpha-helices and a four-stranded beta-sheet, similar to structures of the class of helix-turn-helix DNA binding proteins first found in the catabolite activator protein of Escherichia coli. NMR and mutagenesis experiments suggest that in comparison to structurally related proteins, the ets domain uses a new variation of the helix-turn-helix motif for binding to DNA.

Amino Acid Sequence↗
PubMed1994

[Reproducibility of a self-administered questionnaire for dietary habits, smoking, and drinking].

Reproducibility of results from a self-administered questionnaire on dietary habits (the frequency of taking various foods and eating habits), smoking and drinking was examined to study the reliability of the questionnaire, stability of lifestyle, and the validity of the questionnaire in assessing lifestyle as a risk factor in chronic diseases. The study sample included 120 males and 173 females in a rural town in Kyoto Prefecture, who participated in a series of three health examinations in 1988, 1989, and 1992. A survey using the same questionnaire was performed before each health examination. Reproducibility was assessed by correlation (Spearman's rank correlation coefficient or kappa coefficient), exact agreement of category answered, and comparison of mean frequency. An attempt was made to separate reliability and stability from reproducibility using the data from the questionnaire obtained in the three years. Good reproducibility for one-year and four-year intervals was found for foods taken habitually or often (boiled rice, cooked rice gruel with tea, milk, coffee, fruits and bread), and habits (eating breakfast, some eating habits, smoking and drinking). The same was also found for cigarette or alcohol consumption among current consumers except that cigarette consumption over a four-year interval was more likely to change. The reliability of the questionnaire and stability of these items were considered satisfactory, suggesting that the questionnaire was a valid method of assessing long-term lifestyle. Poor reproducibility of results regarding consumption of green-yellow and other vegetables indicated both poor reliability and a change in consumption over four years, and suggested poor validity. However, disagreement in more than one category of vegetables was not large and misclassification in assessing them as risk factors and changes in frequency of consumption may not be large either. Although correlation coefficients for the items of dairy food and eating snacks were fair, disagreement in more than one category was relatively large which may have caused misclassification. The mean frequency of consumption of pickles and fishpaste, ham or sausage significantly decreased over the four year interval. This may reflect the influence of health education on reducing salt intake.

Adult↗
PubMed1994

Synthesis and characterization of anti-idiotypic anti-T4 antibodies.

We injected rabbits with purified monoclonal murine immunoglobulin (IgG1) or polyclonal antithyroxine antibodies (anti-T4) and polyclonal anti-triiodothyroacetic acid (anti-Triac) antibodies to stimulate the production of anti-idiotypic antibodies. Purified immunoglobulins from all five rabbits immunized with monoclonal primary antibodies were able to inhibit the interaction between [125I]T4 and the primary antibody. The preimmune sera were inactive. This effect was not due to endogenous T4 contamination or contamination with the injected primary antibody. Half-maximal inhibition of binding of primary antibody with anti-idiotype was between 1.6 and 30 micrograms of total immunoglobulins. Addition of normal mouse IgG1 did not alter the inhibitory effect of the anti-idiotypic antibody, suggesting that this effect is specific. These anti-idiotypic antibodies reacted differently with different polyclonal antibodies, reflecting the heterogeneous nature of polyclonal antibody populations. Polyclonal antibodies were less effective in stimulating anti-idiotypic antibody production. One polyclonal anti-T4 and one anti-Triac antibody produced weak anti-idiotypic antibody that had to be used at a concentration of > 600 micrograms of total immunoglobulins to be inhibitory. Both inhibited the binding of T4 to the monoclonal anti-T4 antibody. However, they were ineffective in inhibiting the function of their own antigen, the polyclonal anti-T4 or anti-Triac antibody. We tested the most potent anti-idiotypic antibodies for their ability to compete with T4 for other T4-binding proteins. Specific inhibition of T4 binding to thyroid-binding globulin was observed with half-maximal effect at approximately 450 micrograms of total IgG.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

[The effect of astragalus polysaccharides (APS) on cell mediated immunity (CMI) in burned mice].

In this paper, the changes in CMI in mice were determined after burn injury, and the effects of APS on CMI of burned mice were investigated in vivo. The results showed that on day 6 postburn, spleen index and thymus index were reduced, T lymphocyte transformation and interleukin 2 (IL-2) production were suppressed. Furthermore, the serum and macrophages from burned mice showed significant suppressive activity upon T lymphocyte transformation in vitro, and suppressive index (SI) of suppressor T cell (Ts) was greater than that of normal controls. Intraperitoneal administration of APS (250mg/kg daily, from day 0 to 5 could restore spleen index and thymus index of burned mice, reverse the suppression of T lymphocyte transformation and IL-2 production, reduce remarkably the suppressive activity of serum, macrophages and Ts. It is suggested that (1) burn injury-induced suppression of CMI may be related to the augmented suppressive activity of serum, macrophages and Ts; (2) administration of APS may restore the impaired CMI after burn injury by reducing the suppressive activity of postburn serum, macrophages and Ts.

Animals↗
PubMed1994

[Burden of cigarette smoking on medical costs paid by national health insurance in a rural town].

This study examined the direct association between medical costs and cigarette smoking and modification of interest in visiting medical facilities. The study sample consisted of 966 males 30 years of age or older in a rural town in Kyoto Prefecture, who were members of the National Health Insurance. The subjects were respondents to a previous questionnaire about smoking in February, 1989. There were 544 current smokers, 226 ex-smokers and 141 nonsmokers. Fifty-five subjects did not answer the question about smoking habits. Outpatient medical costs paid by National Health Insurance for the fiscal year 1989 were analyzed. Average medical costs of ex-smokers were the highest of all groups-current, ex-, and non-smokers (30-49, 50-69, and 70+ years of age). Those of current smokers and of the combined current or ex-smokers group were higher than those of non-smokers (30-49 and 50-69 years of age). None of these differences were significant by nonparametric test. The effect of smoking on medical costs was evaluated by odds ratio of the largest class of costs (50,000+ yen for 30-49 years of age, 200,000+ yen for 50-69 years of age, and 500,000+ yen for 70+ years of age) for various types of smokers compared with non-smokers by logistic regression. The odds ratios of current, ex-, and current or ex-smokers 30-49 and 50-69 years of age were between 2 to 3, but not significant. The odds ratio of subjects 70 years of age or older was smaller than unity and not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Genetic fusion of subunits of a dimeric protein substantially enhances its stability and rate of folding.

The gene V protein of bacteriophage f1 is a single-stranded DNA and RNA-binding protein composed of two identical subunits. We have constructed single-chain variants of the protein using short peptide linkers of five or six amino acids to connect the carboxyl terminus of one monomer to the amino terminus of the second monomer. The resulting subunit-fusion gene V proteins were found to bind single-stranded DNA nearly as tightly as the wild-type protein. Denaturation measurements show that the subunit-fusion gene V proteins are 5 kcal/mol (1 kcal = 4.18 kJ) more stable than the wild-type protein at a protein concentration of 10 microM. The rate of unfolding of the protein is essentially unaffected by the fusion of monomeric subunits, whereas the rate of folding is greatly enhanced. Our results suggest a simple way of obtaining a substantial thermodynamic stabilization for some oligomeric proteins.

Coliphages↗
PubMed1993

Equilibrium denaturation of recombinant human FK binding protein in urea.

The equilibrium folding behavior of recombinant human FK-binding protein, a peptidyl-prolyl cis-trans-isomerase, was examined by urea-induced denaturation using probes of protein structure including intrinsic tryptophan fluorescence, second-derivative UV absorbance, CD, and NMR. All optical probes of protein structure indicate that FKBP is capable of folding reversibly. The second-derivative UV absorbance and CD probes of the structure exhibited urea denaturation transitions at approximately 4.3 M urea. The fluorescence of the single protein tryptophan is quenched in the folded state. During the unfolding-folding transition, the unquenching of tryptophan fluorescence occurs at a slightly lower urea concentration (3.9 M urea) than the changes observed for the other optical probes of folding. These probes of structure demonstrate little dependence on protein concentration in the range of 0.2- approximately 3 mg/mL across the urea-induced denaturation transition. The reversibility of the unfolding-folding transition was confirmed from two-dimensional 15N/1H heteronuclear single-quantum coherence (HSQC) spectra of [U-15N]FKBP. In addition, the native-denatured transitions for 57 individual amino acids were determined from an analysis of these spectra acquired at different urea concentrations. Analysis of the transitions for all clearly observable HSQC cross peaks for residues distributed throughout the protein and comparison to the optical folding transitions, indicate that FKBP global folding is consistent with a two-state process. Although direct measurement of FKBP catalytic activity in urea was complex, enzyme activity was observed up to the beginning of the FKBP urea-denaturation transition.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Micromanipulation of chromosomes in PTK2 cells using laser microsurgery (optical scalpel) in combination with laser-induced optical force (optical tweezers).

An optical scalpel and optical tweezer have been combined to perform intracellular microsurgery and micromanipulation in vivo. When only laser microsurgery was performed on metaphase chromosomes, the dissected sister chromatid fragments drifted off to either the side of the spindle or completely off the spindle. At anaphase the fragments separated and the two arms generally moved to their respective daughter cells. When the chromosome arm was cut during anaphase A and B, the distal chromosome fragment separated from the rest of the chromosome and moved toward the pole, following the proximal chromosome fragment. Distal chromosome fragments laser-dissected during metaphase were held together throughout anaphase using the optical trap. Optical trapping of dissected chromosome fragments during anaphase A and B inhibited movement of the chromosome fragment to its pole. As a result, the trapped chromosome fragments were (1) incorporated into the opposite daughter cell, (2) lost in the cleavage furrow during cytokinesis, or (3) eventually incorporated into the correct daughter cell. These results indicate that optical traps are effective in holding laser-dissected chromosome fragments throughout mitosis. This new tool should be useful for studies on chromosome movement and cell genetics.

Animals↗
PubMed1993

Inhibition by genistein of prolactin-induced Nb2 lymphoma cell mitogenesis.

Tyrosine kinase activation in mediating the mitogenic action of prolactin (PRL) has been evaluated. Use was made of genistein, a tyrosine kinase antagonist, and cultured rat Nb2 lymphoma cells, i.e. the lactogen-dependent Nb2-11 line and a lactogen-independent subline, Nb2-SFJCD1. Genistein was found to be a potent growth-inhibitor for both lines, inhibiting 3H-thymidine incorporation in Nb2-11 and Nb2-SFJCD1 cells with IC50s of 4.2 and 6.7 micrograms/ml, respectively. Genistein also inhibited expression and translation of the heat shock protein 70 gene and pp40 protein substrate phosphorylation which, in Nb2-11 cells, followed PRL addition within minutes. Genistein inhibition of DNA synthesis in G1-arrested Nb2-11 cells was most pronounced if the agent was added within 1 h of PRL treatment. The results indicate that, while both Nb2 cell lines have a general growth requirement for tyrosyl phosphorylation, the early, PRL-induced tyrosine kinase activation is a component of the PRL mitogenic signal transduction pathway.

Animals↗
PubMed1993

Optical trapping for chromosome manipulation: a wavelength dependence of induced chromosome bridges.

Using a tunable titanium-sapphire laser, we have compared different wavelengths (from 700 to 840 nm) for their utility in optical trapping of chromosomes in mitotic rat kangaroo Potorous tridactylus (PtK2) cells. It was found that irradiation with a near-infrared light induces the sticking together of chromosome shoulders. The attached chromatids failed to separate, or separated with significant delay and formed a chromosome bridge during anaphase. Using this bridge (and induced c-mitosis) as a reference, we compared the action of different wavelengths (from 700 to 840 nm). Chromosomes were irradiated at metaphase and the cells were observed until the end of cytokinesis. Chromosomes were irradiated for different periods of time, using 130 mW of power at the objective focal plane. The biological responses observed after optical trapping were: (1) normal cell division, (2) formation of a temporary chromosome bridge, (3) formation of a permanent chromosome bridge, (4) complete blockage of chromosome separation (c-mitosis). The chromosomes were found to have a maximal sensitivity to 760-765 nm light and minimal sensitivity to 700 and 800-820 nm light. Cells with chromosomes irradiated for a long time, using wavelength 760-765 nm, generally were incapable of going through anaphase and remained in c-mitosis. We conclude that the optimal wavelengths for optical trapping are 700 and 800-820 nm.

Animals↗
PubMed1993

Comparison of Fo extraction methods for high-precision voice perturbation measurements.

Voice perturbation measures, such as jitter and shimmer, depend on accurate extraction of fundamental frequency (Fo) and amplitude of various waveform types. The extraction method directly affects the accuracy of the measures, particularly if several waveform types (with or without formant structure) are under consideration and if noise and modulation are present in the signal. For frequency perturbation, high precision is defined here as the ability to extract Fo to +/- 0.01% under conditions of noise and modulation. Three Fo-extraction methods and their software implementations are discussed and compared. The methods are cycle-to-cycle waveform matching, zero-crossing and peak-picking. Interpolation between samples is added to make the extractions more accurate and reliable. The sensitivity of the methods to different parameters such as sampling frequency, mean Fo, signal-to-noise ratio, frequency modulation, and amplitude modulation are explored.

Electronic Data Processing↗
PubMed1993

Roles of multiple glucose transporters in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, TRK1 and TRK2 are required for high- and low-affinity K+ transport. Among suppressors of the K+ transport defect in trk1 delta trk2 delta cells, we have identified members of the sugar transporter gene superfamily. One suppressor encodes the previously identified glucose transporter HXT1, and another encodes a new member of this family, HXT3. The inferred amino acid sequence of HXT3 is 87% identical to that of HXT1, 64% identical to that of HXT2, and 32% identical to that of SNF3. Like HXT1 and HXT2, overexpression of HXT3 in snf3 delta cells confers growth on low-glucose or raffinose media. The function of another new member of the HXT superfamily, HXT4 (previously identified by its ability to suppress the snf3 delta phenotype; L. Bisson, personal communication), was revealed in experiments that deleted all possible combinations of the five members of the glucose transporter gene family. Neither SNF3, HXT1, HXT2, HXT3, nor HXT4 is essential for viability. snf3 delta hxt1 delta hxt2 delta hxt3 delta hxt4 delta cells are unable to grow on media containing high concentrations of glucose (5%) but can grow on low-glucose (0.5%) media, revealing the presence of a sixth transporter that is itself glucose repressible. This transporter may be negatively regulated by SNF3 since expression of SNF3 abolishes growth of hxt1 delta hxt2 delta hxt3 delta hxt4 delta cells on low-glucose medium. HXT1, HXT2, HXT3, and HXT4 can function independently: expression of any one of these genes is sufficient to confer growth on medium containing at least 1% glucose. A synergistic relationship between SNF3 and each of the HXT genes is suggested by the observation that SNF2 hxt1 delta hxt2 delta hxt3 delta hxt4 delta cells and snf3 delta HXT1 HXT2 HXT3 HXT4 cells are unable to grow on raffinose (low fructose) yet SNF3 in combination with any single HXT gene is sufficient for growth on raffinose. HXT1 and HXT3 are differentially regulated. HXT1::lacZ is maximally expressed during exponential growth whereas HXT3::lacZ is maximally expressed after entry into stationary phase.

Amino Acid Sequence↗
PubMed1993

Comparison of the metabolic and endocrine effects of 3,5,3'-triiodothyroacetic acid and thyroxine.

To test the hypothesis that 3,5,3'-triiodothyroacetic acid (Triac) is more active as a TSH suppressor than on peripheral parameters of thyroid hormone action, the following parameters were studied: basal metabolic rate, sleeping energy expenditure (SEE), sex hormone-binding globulin, and cholesterol. In a double blind trial, 14 subjects received during 3 weeks (phase 1) 180 micrograms T4 or 1700 micrograms Triac daily, divided into 3 doses, to suppress thyroidal secretion. The dosage was doubled for the next 3 weeks (phase 2). Under T4 treatment, TSH reached 0.11 mU/L during phase 1 and less than 0.03 mU/L during phase 2. With Triac, a marked TSH inhibition occurred after 1 week (0.17 mU/L), followed by an escape during the following 2 weeks (0.63 mU/L). During phase 2, an almost complete TSH suppression was obtained (0.03 mU/L). Both Triac doses suppressed endogenous thyroid hormone secretion, as evidenced by T4 and rT3 levels. Both substances induced a 2-fold stimulation of sex hormone-binding globulin during phase 2. Serum cholesterol decreased similarly, without affecting the high/low density lipoprotein ratio. T4 increased SEE by 4.1% and 8.5% during phases 1 and 2. Triac failed to induce the expected peripheral metabolic responses of the thyroid hormones, as demonstrated by an unchanged SEE and basal metabolic rate. These results clearly show a preferential action of Triac on TSH suppression.

Basal Metabolism↗
PubMed1993

Astral and spindle forces in PtK2 cells during anaphase B: a laser microbeam study.

Rat kangaroo kidney epithelium (PtK2) cells develop prominent asters and spindles during anaphase B of mitosis. It has been shown that severing the spindle at early anaphase B in living PtK1 cells results in a dramatic increase in the rate of pole-pole separation. This result suggested that the asters pull on the spindle poles, putting tension on the spindle, while the spindle acts as a governor, limiting the rate of pole separation. To further test these inferences, we used a UV-laser microbeam to damage one of the two asters in living PtK2 cells at early anaphase B and monitored the effects on individual spindle pole movements, pole-pole separation rates and astral microtubules (MTs). Irradiation at the estimated position of a centrosome greatly reduced its array of astral MTs and nearly stopped the movement of the irradiated pole, whereas the sister pole retained its normal array of astral MTs and actually accelerated. Control irradiations, either close to the estimated position of the centrosome or beside the spindle at the equator, had little or no effect on either spindle pole movements or astral MTs. These results support the inferences that during anaphase B in living PtK cells, the central spindle is under tension generated by pulling forces in the asters (presumably MT-mediated) and that the spindle generates counterforces that limit the rate of pole separation. The results also suggest that the central spindle in living PtK cells may be able to generate a pushing force.

Anaphase↗
PubMed1993

[Comparison of a rural town and a fishing town: diet and circulatory system diseases].

We report a comparative study of the Standardized Mortality Ratio (SMR) for circulatory system diseases and diet in a rural town and a fishing town in Kyoto Prefecture. SMR was assessed during the 5-year period from 1983 through 1987, and compared with the standard age- and sex-adjusted demographic and mortality statistics compiled by the National Census Bureau of Japan in 1985. A food frequency questionnaire in which the respondents evaluated their food consumption during the previous 1-year period was used to assess diet. The questionnaire was administered during February 1989 in the rural town and during February 1990 in the fishing town. In comparison with the standard statistics, SMR was higher in the rural town and lower in the fishing town. The inhabitants of the fishing town more frequently consumed low-fat and low-sodium foods, such as fish, potatoes, tofu, and green, yellow and other vegetables, and less frequently consumed high-fat and high-sodium foods, such as meat, fried food, pickles, than did the inhabitants of the rural town. The residents of the fishing town also consumed a greater variety of foods in one week. The two towns differ in geography and economic structure, and their inhabitants have different life-styles and eating habits. The lower SMR for circulatory system diseases in the fishing town may be related to the greater consumption of fish and vegetables with lower meat and salt intake, as well as the balanced of diet.

Adult↗