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Biomedical subjects

C Wu

Publications and source records attributed to C Wu.

At least 523 records · Page 29Linked to original sources
PubMed1991

Cloning and characterization of two mouse heat shock factors with distinct inducible and constitutive DNA-binding ability.

We have cloned two distinct mouse heat shock transcription factor genes, mHSF1 and mHSF2. The mHSF1 and mHSF2 open reading frames are similar in size, containing 503 and 517 amino acids, respectively. Although mHSF1 and mHSF2 are quite divergent overall (only 38% identity), they display extensive homology in the DNA-binding and oligomerization domains that are conserved in the heat shock factors of Saccharomyces cerevisiae, Kluyveromyces lactis, Drosophila, tomato, and human. The ability of these two mouse heat shock factors to bind to the heat shock element (HSE) is regulated by heat. mHSF1 is expressed in an in vitro translation system in an inactive form that is activated to DNA binding by incubation at temperatures greater than 41 degrees C, the same temperatures that activate heat shock factor DNA binding and the stress response in mouse cells in vivo. mHSF2, on the other hand, is expressed in a form that binds DNA constitutively but loses DNA binding by incubation at greater than 41 degrees C. Both mHSF1 and mHSF2 are encoded by single-copy genes, and neither is transcriptionally regulated by heat shock. However, there is a striking difference in the levels of mHSF1 mRNA in different tissues of the mouse.

Amino Acid Sequence↗
PubMed1991

Issues surrounding the assessment of the genetic determinants of drugs as reinforcing stimuli.

A wide variety of drugs used in medicine and on a non-prescription basis have abuse liability. However, not all psychoactive drugs have demonstrable reinforcing properties either in animal models or in humans. In order to predict the abuse liability of a compound or to understand determinants of the abuse liability, several animal testing procedures have been developed. These procedures include tests for physical dependence, tolerance, disruption of ongoing behaviors, discriminative stimulus properties, and the direct or indirect assessment of the reinforcement. While tests for the production of tolerance and physical dependence may not predict abuse liability, they would significantly modify the abuse risk. This paper will focus on the methods available for the assessment of the reinforcing properties and the advantages of using genetically defined mice to better understand the determinants of the reinforcing properties and to isolate phenotypes that are hyper-responsive and hypo-responsive to the reinforcing properties of drugs under study. Examples of genetically determined differences are provided and areas of inadequate information are discussed.

Animals↗
PubMed1991

[Study of the mechanism of gastrodin and derivatives of gastrodigenin].

The tritiated alpha-isobutylhydroxybenzyl alcohol (3H-G018) was found to be able to bind benzodiazepine (BZ) receptor on the rat brain membrane. The 125I labeled G-018 also had the similar binding activity with this receptor. In the present investigation, we observed that gastrodigenin and its derivatives inhibited the 125I-G018 binding of BZ receptor competitively, but no inhibition was observed with gastrodin. The results suggested that Gastrodigenin was bound to BZ receptor, and otherwise, gastrodin would have no direct interaction with BZ receptor. Probably, it might metabolize into gastrodigenin in vivo, and then got through the blood brain barrier and bound to BZ receptor, which mediated its pharmacological effects on the central nervous system.

Animals↗
PubMed1991

[Determination of trace chloride and sulfate in drugs by ion chromatography].

Chloride and sulfate in magnesium trisilicate, activated charcoal, vesnarinone and bendazac were determined by the IC conductimetric detection. Analysis were performed by using a separating column (100 x 6 mm i.d.) packed with anion exchanger and with a stripper column (100 x 6 mm i.d.); 1.4 mmol/L Na2CO3 and 1.4 mmol/L Na2CO3-0.75 mmol/L NaHCO3 were used as eluents respectively. The peak height was linear with concentration from 10(-6) to 10(-3) mol/L for Cl- and from 10(-5) to 10(-3) mol/L for SO4(2-). Results showed no significant difference as compared with those determined by the CHP (1985) and CHP (1990) appendices methods. The IC method is specific, sensitive, simple and rapid.

Charcoal↗
PubMed1991

[Anti-oxidation of Paecilomyces Sinensis (S. Pnov.)].

This paper indicates that Paecilomyces sinensis ig 3g/kg/dx14 increases the amount of superoxide dismutase in the liver tissues of mice; that Paecilomyces sinensis is similar to natural Cordyceps sinensis in inhibiting the production of Lpo and increasing the amount of superoxide dismutase in the liver homogenates of mice in vitro. In addition Paecilomyces sinensis can also increase the amount of glutathione peroxidase in the liver homogenates of mice in vitro.

Animals↗
PubMed1990

Molecular cloning and expression of a hexameric Drosophila heat shock factor subject to negative regulation.

We report the cloning of the transcriptional activator of heat shock genes, HSF, from Drosophila. The predicted sequence of Drosophila HSF protein is surprisingly divergent from that of yeast HSF, except in regions important for DNA binding and oligomerization. A segment of the DNA binding domain of HSF bears an intriguing similarity to the putative DNA recognition helix of bacterial sigma factors, while the oligomerization domain contains an unusual arrangement of conserved hydrophobic heptad repeats. Drosophila HSF produced in E. coli under nonshock conditions forms a hexamer that binds specifically to DNA with high affinity and activates transcription from a heat shock promoter in vitro. In contrast, when HSF is expressed in Xenopus oocytes, maximal DNA binding affinity is observed only after heat shock induction. These results suggest that Drosophila HSF has an intrinsic affinity for DNA, which is repressed under nonshock conditions in vivo.

Amino Acid Sequence↗
PubMed1990

Antibody-mediated activation of Drosophila heat shock factor in vitro.

Eukaryotic cells respond to elevated temperatures by rapidly activating the expression of heat shock genes. Central to this activation is heat shock-inducible binding of the transcriptional activator, termed heat shock factor (HSF), to common regulatory elements, which are located upstream of all heat shock genes. The DNA binding activity of the inactive form of Drosophila HSF was induced in vitro by treatment with polyclonal antibodies to the purified, in vivo-activated factor. This finding, together with observations that high temperature and low pH activate HSF binding in vitro, suggests that the inactive form of HSF can directly recognize and transduce the heat shock signal without undergoing a covalent modification of protein structure.

Animals↗
PubMed1990

Electrophoresis and movements of fluorescence pattern after photobleaching of large DNA fragments in agarose gels.

By combining electrophoresis with movements of fluorescence pattern after photobleaching (MOFPAP), which is abbreviated as EMOFPAP, we are able to measure electrophoretic mobilities of large DNA fragments in an agarose gel within a fairly short time scale (about 10 min or even down to 1 min). The new method represents a significant improvement in experiment time when compared with the time (typically on the order of hours) required to determine the average electrophoretic mobility of large DNA fragments in agarose gels by means of either conventional gel electrophoresis or pulsed-field gel electrophoresis. In this article, we present the EMOFPAP experimental setup and consider optical conditions, including beam profile geometry and fluorescence pattern formation. A realistic formula that can explain the parameters governing the EMOFPAP method using our present optical setup has been derived. A comparison of results between experimental and computer simulation data is made, and an optimization of the EMOFPAP method is proposed.

DNA↗
PubMed1990

A sequence-specific DNA-binding protein that activates fushi tarazu segmentation gene expression.

The Drosophila segmentation gene fushi tarazu (ftz) is expressed at the cellular blastoderm stage in a pattern of seven transverse stripes; the stripes lie out of register with the segmental primordia, spanning alternate segmental boundaries. The zebra element, a 740-bp DNA sequence upstream of the ftz translational start, directs striped expression of lacZ when introduced into the fly genome. We have purified to homogeneity a sequence-specific DNA-binding factor, FTZ-F1, that binds to two sites located within the zebra element and to two sites within the ftz protein-coding sequence. FTZ-F1 DNA-binding activity is first detected in extracts of 1.5- to 4-hr embryos, coincident with the time of ftz expression in stripes; the activity then diminishes before reappearing during late embryo, larval, and adult stages. When one of the FTZ-F1-binding sequences in the zebra element is mutated by 2- or 4-base substitutions, the binding to FTZ-F1 is disrupted in vitro, and the intensity of lacZ expression is reduced in transformed embryos, especially in stripes 1, 2, 3, and 6. The results suggest that FTZ-F1 is a transcriptional activator necessary for the proper expression of the ftz gene.

Animals↗
PubMed1990

Complex modes of heat shock factor activation.

Eucaryotic organisms respond to elevated environmental temperatures by rapidly activating the expression of heat shock genes. The transcriptional activation of heat shock genes is mediated by a conserved upstream regulatory sequence, the heat shock element (HSE). Using an HSE-binding assay, we show that a cellular factor present in a range of vertebrate species binds specifically to the HSE. This factor is presumably the transcriptional activator of heat shock genes, heat shock factor (HSF). In vertebrates, the binding of HSF to the HSE was induced when cells were subjected to heat shock at high temperatures, even in the absence of protein synthesis. Under mild heat shock conditions, HSF binding was induced to a lesser extent, but this induction required protein synthesis, suggesting that synthesis of HSF itself, or an activating factor, is necessary for response to heat shock at intermediate temperatures. The inducibility of HSF binding in higher eucaryotes is contrasted with constitutive HSF binding activity in fungi. It appears that despite conservation of the HSE in evolution, the means by which HSF is activated to bind DNA in higher and lower eucaryotes may have diverged.

Animals↗
PubMed1990

[A new serotype of Salmonella IIIb].

An enterobacterium culture, S3188, providing with Salmonella biological characteristics, except exhibiting indole positive reaction, was isolated from the intestinal content of reptile a snake. It utilized malonate, did not ferment dulcitol, it attacked lactose promptly, and ONPG positive. H antigens appeared diphasic. By cross agglutination and absorption tests, it was demonstrated that the antigenic formula of this strain is 53:1, Z13:e, n,(Z15)... It was found to be a new serotype of Salmonella IIIb.

Animals↗
PubMed1990

[Ion-paired high performance liquid chromatographic determination of mitoxantrone hydrochloride injection].

Mitoxantrone (DHAQ) is a new anti-cancer agent. The ion-pair HPLC method to determine mitoxantrone hydrochloride injection was proposed. Mitoxantrone can be separated on Zorbax-ODS column with methanol-water-formic acid (450:50:1.5) containing 3.605g SDS as mobile phase. The pH of mobile phase was adjusted to 2.7. The flow rate was 1.0 ml/min and detection was at wavelength of 254 nm, providing a detection limit of 1ng (r/n, 3:1) of DHAQ. DHAQ was determined by peak area measurement with ametantrone as internal standard. The rectilinear calibration graph in the range of 1-10 micrograms of DHAQ was obtained (r = 0.999 2). The average recovery was 99.62 +/- 2.36% (n = 10), and the results were not interfered by the other ingredients in the injection.

Chromatography, High Pressure Liquid↗
PubMed1989

Bending of DNA by gene-regulatory proteins: construction and use of a DNA bending vector.

The binding of a protein to its specific sequence, borne on a DNA fragment, retards the mobility of the fragment in a characteristic way during gel electrophoresis. If the protein induces bending in the DNA, the contortion can also be monitored by gel electrophoresis, because the amount of retardation of the mobility of the DNA-protein complex is dependent upon the position and the degree of the bend induced in the DNA fragment [Wu and Crothers, Nature 308 (1984) 509-513]. We have constructed a plasmid, pBend2, which can generate a large number of DNA fragments of identical length in which the protein-binding nucleotide sequence is located in circular permutations. The vector contains two identical DNA segments containing 17 restriction sites in a direct repeat spanning a central region containing cloning sites. The protein-binding sequence is inserted at one of these cloning sites. To investigate the functional significance of bending, we have compared, using pBend2, the cAMP.cAMP-receptor protein (CPR)-induced bending of CRP-binding sites found in five different genes of Escherichia coli. We have also shown that the bacteriophage lambda 0R1 operator DNA is bent when complexed with the CI or Cro repressor of the phage.

Bacteriophage lambda↗
PubMed1989

Quality assurance and precision of dual photon absorptiometry in bone mineral measurement.

Dual photon absorptiometry (DPA) has evolved as a powerful technique in measuring bone mineral density (BMD) to assess osteoporosis and metabolic bone diseases in recent years. We introduced the first installation of DPA instrument into this country in Aug. 1987. Since the comparison among longitudinal BMD values influences the diagnosis, monitoring and medical decision-making, high precision of the system performance and strict quality assurance program are prerequisite for judgment of the difference between two successive measurements. However, the automation and black-box software design of the instrument make users gain very little knowledge how the instruments acquire the long-term system reliability. The first part of this study was designed to establish a standardized procedure to evaluate the long-term quality of the DPA instrument. Our instrument was proved to have stable sensitivity, resolution, accuracy and reproducibility in the four months of study. Three subjects with different BMD levels were scanned to evaluate the intraobserver and interobserver errors in BMD analysis expected in our laboratory (2.2 and 1.6% at 95% confidence level, respectively). The results indicated that reanalyzing the same scan by either of the two observers would produce a BMD precision error within 2.2% at a 95% confidence level. Serial scans of 7 normal volunteers within five weeks were then conducted to evaluate the overall precision of the BMD measurements. Our findings indicated that two scans would be considered as having a real BMD change if they differ by more than 3.3% at a 95% confidence level. There are at least five sets of DPA instruments that have been installed in Taiwan presently.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗